Methods and systems for detection of protein-dna interactions using proximity ligation

ABSTRACT

The present disclosure provides systems and methods that facilitate, at the single cell level, the linking of information from multiple different antibodies (e.g., antibodies specific for different proteins) to the genomic locations of the protein binding sites, while being able to distinguish these distinct events between antibodies.

CROSS-REFERENCE

This is a continuation application of International Patent ApplicationNo. PCT/US2019/046940, filed Aug. 16, 2019, which claims benefit of U.S.Provisional Application No. 62/720,091, filed Aug. 20, 2018, and U.S.Provisional Application No. 62/787,997, filed Jan. 3, 2019, each ofwhich applications is entirely incorporated herein by reference.

BACKGROUND

The mapping of protein-DNA interactions has conventionally beenaccomplished using procedures like ChIP-seq (chromatinimmunoprecipitation (ChIP) with sequencing) in which DNA-bound proteinsare immuno-precipitated using a specific antibody. The co-precipitated,antibody-bound DNA is then typically purified and sequenced to allow theidentification of genome-wide DNA binding sites of a specific protein.ChIP-seq has been used to map a number of different protein-DNAinteractions, including transcription factors (TFs), post-translationalmodifications (e.g., histones) and enzymes (e.g., RNA polymerase II).

Conventional ChIP-seq protocols typically analyze protein-DNAinteractions by: (1) cell lysis, (2) solubilization and fragmentation ofDNA, and (3) immuno-precipitation of a target protein with an antibodyfollowed by affinity purification of the antibody-bound DNA complexes.The challenge for combining these steps into a single workflow that isamenable to single-cell analysis has limited the adoption of thisprocedure into the single cell context. To date, only a limited set ofefforts have been devised to overcome these limitations. However, forall of the proposed modifications to the ChIP procedure to achieve moresensitive and efficient detection, none are able to interrogate multipleproteins simultaneously.

To overcome this limitation, the assay must be able to link informationfrom multiple different antibodies to the genomic locations of theprotein binding sites, while being able to distinguish these distinctevents between antibodies. The following disclosure provides methods andsystems that overcome these limitations and allow for the simultaneousdetection of multiple protein-nucleic interactions in a single cellcontext.

SUMMARY

In one aspect, a method is provided comprising: (a) fragmentingchromatin to generate a plurality of chromatin fragments; (b) taggingthe plurality of chromatin fragments with a first tag to generate aplurality of first tagged chromatin fragments; (c) binding an affinitymolecule to a protein or a peptide associated with at least one taggedchromatin fragment of the plurality of first tagged chromatin fragments,wherein the affinity molecule is coupled to a second tag; and (d)coupling the first tag to the second tag to generate a second taggedchromatin fragment. In some cases, the method further comprises, (e)sequencing the second tagged chromatin fragment. In some cases, themethod further comprises, prior to (e), amplifying the second taggedchromatin fragment. In some cases, the fragmenting of (a) and thetagging of (b) comprise a tagmentation reaction. In some cases, thetagmentation reaction is performed by a transposase. In some cases, thetransposase is selected from the group consisting of: a hyperactive Tn5transposase, a MuA transposase, a Vibhar transposase, and Hermes. Insome cases, the first tag is a first oligonucleotide tag and the secondtag is a second oligonucleotide tag. In some cases, the coupling of (d)comprises ligating the first oligonucleotide tag to the secondoligonucleotide tag. In some cases, the ligating further comprises: (i)annealing a first region of the first oligonucleotide tag to a firstregion of the second oligonucleotide tag, wherein the first region ofthe first oligonucleotide tag is complementary to the first region ofthe second oligonucleotide tag; and (ii) ligating the firstoligonucleotide tag to the second oligonucleotide tag. In some cases,the ligating further comprises: (i) annealing a first region of a thirdoligonucleotide tag to a region of the first oligonucleotide tag,wherein the first region of the third oligonucleotide tag iscomplementary to the region of the first oligonucleotide tag; (ii)annealing a second region of the third oligonucleotide tag to a regionof the second oligonucleotide tag, wherein the second region of thethird oligonucleotide tag is complementary to the region of the secondoligonucleotide tag; and (iii) ligating the third oligonucleotide tag tothe first oligonucleotide tag and the second oligonucleotide tag. Insome cases, the third oligonucleotide tag comprises a unique molecularindex, a cell barcode, or both. In some cases, the third oligonucleotideis attached to a surface of a bead. In some cases, the thirdoligonucleotide is releasably attached to the surface of the bead. Insome cases, the bead is a gel bead. In some cases, the bead comprises aplurality of third oligonucleotides, each of the plurality of thirdoligonucleotides comprising: (i) a first barcode unique for eachindividual first tagged chromatin fragment binding thereon; and (ii) asecond barcode unique to the bead. In some cases, the method furthercomprises, prior to (d), partitioning a plurality of cells or cellnuclei into a plurality of partitions, wherein each partition of theplurality of partitions comprises a single cell or cell nucleus. In somecases, the method further comprises, prior to (d), partitioning the beadinto a plurality of partitions, such that each partition of theplurality of partitions contains a single bead. In some cases, thepartition is an emulsion droplet. In some cases, the method furthercomprises, attaching one or more sequencing adapters to the secondtagged chromatin fragment prior to the sequencing of (e). In some cases,the first tag is not unique for each of the plurality of first taggednucleic acid fragments. In some cases, the first tag is attached to afirst end of the plurality of first tagged nucleic acid fragments, thefirst tag is attached to a second end of the plurality of first taggednucleic acid fragments, or both. In some cases, the affinity molecule isselected from the group consisting of: an antibody or an antibodyfragment, a protein, a peptide, and an aptamer. In some cases, theprotein or peptide associated with the at least one tagged nucleic acidfragment is a transcription factor, a histone, a histone modification,an epigenetic regulator, or any combination thereof. In some cases, thesecond tag comprises an affinity molecule barcode. In some cases, theaffinity molecule barcode is unique for a type of affinity molecule. Insome cases, the method further comprises, prior to (a), permeabilizingone or more cells or cell nuclei. In some cases, the one or more cellsor cell nuclei are unfixed cells or unfixed cell nuclei. In some cases,the fragmenting occurs at open regions of chromatin. In some cases, theopen regions of chromatin comprise euchromatin. In some cases, theplurality of nucleic acid fragments are not diluted prior to (a) or (b).In some cases, the fragmenting of (a) and said tagging of (b) areperformed inside an intact cell or cell nucleus. In some cases, themethod further comprises, binding a plurality of affinity molecules to aplurality of proteins or peptides associated with said first taggednucleic acid fragments. In some cases, the plurality of affinitymolecules comprise a plurality of different affinity molecules capableof binding to different proteins or peptides associated with the firsttagged nucleic acid fragments. In some cases, the plurality of differentaffinity molecules comprises at least two different affinity molecules.

Another aspect of the present disclosure provides a non-transitorycomputer readable medium comprising machine executable code that, uponexecution by one or more computer processors, implements any of themethods above or elsewhere herein.

Another aspect of the present disclosure provides a system comprisingone or more computer processors and computer memory coupled thereto. Thecomputer memory comprises machine executable code that, upon executionby the one or more computer processors, implements any of the methodsabove or elsewhere herein.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.To the extent publications and patents or patent applicationsincorporated by reference contradict the disclosure contained in thespecification, the specification is intended to supersede and/or takeprecedence over any such contradictory material.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings (also “Figure” and “FIG.” herein), of which:

FIG. 1 shows an example of a microfluidic channel structure forpartitioning individual biological particles.

FIG. 2 shows an example of a microfluidic channel structure fordelivering barcode carrying beads to droplets.

FIG. 3 shows an example of a microfluidic channel structure forco-partitioning biological particles and reagents.

FIG. 4 shows an example of a microfluidic channel structure for thecontrolled partitioning of beads into discrete droplets.

FIG. 5 shows an example of a microfluidic channel structure forincreased droplet generation throughput.

FIG. 6 shows another example of a microfluidic channel structure forincreased droplet generation throughput.

FIG. 7A shows a cross-section view of another example of a microfluidicchannel structure with a geometric feature for controlled partitioning.FIG. 7B shows a perspective view of the channel structure of FIG. 7A.

FIG. 8 illustrates an example of a barcode carrying bead.

FIG. 9 shows a computer system that is programmed or otherwiseconfigured to implement methods provided herein.

FIG. 10 shows an exemplary processing scheme to link information frommultiple different antibodies to the genomic locations of the proteinbinding sites.

FIG. 11 shows representative steps of an exemplary processing scheme tolink information from multiple different antibodies to the genomiclocations of the protein binding sites.

FIG. 12 shows an exemplary alternative processing scheme to linkinformation from multiple different antibodies to the genomic locationsof the protein binding sites.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed.

Where values are described as ranges, it will be understood that suchdisclosure includes the disclosure of all possible sub-ranges withinsuch ranges, as well as specific numerical values that fall within suchranges irrespective of whether a specific numerical value or specificsub-range is expressly stated.

The term “barcode,” as used herein, generally refers to a label, oridentifier, that conveys or is capable of conveying information about ananalyte. A barcode can be part of an analyte. A barcode can beindependent of an analyte. A barcode can be a tag attached to an analyte(e.g., nucleic acid molecule) or a combination of the tag in addition toan endogenous characteristic of the analyte (e.g., size of the analyteor end sequence(s)). A barcode may be unique. Barcodes can have avariety of different formats. For example, barcodes can include:polynucleotide barcodes; random nucleic acid and/or amino acidsequences; and synthetic nucleic acid and/or amino acid sequences. Abarcode can be attached to an analyte in a reversible or irreversiblemanner. A barcode can be added to, for example, a fragment of adeoxyribonucleic acid (DNA) or ribonucleic acid (RNA) sample before,during, and/or after sequencing of the sample. Barcodes can allow foridentification and/or quantification of individual sequencing-reads.

The term “real time,” as used herein, can refer to a response time ofless than about 1 second, a tenth of a second, a hundredth of a second,a millisecond, or less. The response time may be greater than 1 second.In some instances, real time can refer to simultaneous or substantiallysimultaneous processing, detection or identification.

The term “subject,” as used herein, generally refers to an animal, suchas a mammal (e.g., human) or avian (e.g., bird), or other organism, suchas a plant. For example, the subject can be a vertebrate, a mammal, arodent (e.g., a mouse), a primate, a simian or a human. Animals mayinclude, but are not limited to, farm animals, sport animals, and pets.A subject can be a healthy or asymptomatic individual, an individualthat has or is suspected of having a disease (e.g., cancer) or apre-disposition to the disease, and/or an individual that is in need oftherapy or suspected of needing therapy. A subject can be a patient. Asubject can be a microorganism or microbe (e.g., bacteria, fungi,archaea, viruses).

The term “genome,” as used herein, generally refers to genomicinformation from a subject, which may be, for example, at least aportion or an entirety of a subject's hereditary information. A genomecan be encoded either in DNA or in RNA. A genome can comprise codingregions (e.g., that code for proteins) as well as non-coding regions. Agenome can include the sequence of all chromosomes together in anorganism. For example, the human genome ordinarily has a total of 46chromosomes. The sequence of all of these together may constitute ahuman genome.

The terms “adaptor(s)”, “adapter(s)” and “tag(s)” may be usedsynonymously. An adaptor or tag can be coupled to a polynucleotidesequence to be “tagged” by any approach, including ligation,hybridization, or other approaches.

The term “sequencing,” as used herein, generally refers to methods andtechnologies for determining the sequence of nucleotide bases in one ormore polynucleotides. The polynucleotides can be, for example, nucleicacid molecules such as deoxyribonucleic acid (DNA) or ribonucleic acid(RNA), including variants or derivatives thereof (e.g., single strandedDNA). Sequencing can be performed by various systems currentlyavailable, such as, without limitation, a sequencing system byIllumina®, Pacific Biosciences (PacBio®), Oxford Nanopore®, or LifeTechnologies (Ion Torrent®). Alternatively or in addition, sequencingmay be performed using nucleic acid amplification, polymerase chainreaction (PCR) (e.g., digital PCR, quantitative PCR, or real time PCR),or isothermal amplification. Such systems may provide a plurality of rawgenetic data corresponding to the genetic information of a subject(e.g., human), as generated by the systems from a sample provided by thesubject. In some examples, such systems provide sequencing reads (also“reads” herein). A read may include a string of nucleic acid basescorresponding to a sequence of a nucleic acid molecule that has beensequenced. In some situations, systems and methods provided herein maybe used with proteomic information.

The term “bead,” as used herein, generally refers to a particle. Thebead may be a solid or semi-solid particle. The bead may be a gel bead.The gel bead may include a polymer matrix (e.g., matrix formed bypolymerization or cross-linking). The polymer matrix may include one ormore polymers (e.g., polymers having different functional groups orrepeat units). Polymers in the polymer matrix may be randomly arranged,such as in random copolymers, and/or have ordered structures, such as inblock copolymers. Cross-linking can be via covalent, ionic, or inductiveinteractions, or physical entanglement. The bead may be a macromolecule.The bead may be formed of nucleic acid molecules bound together. Thebead may be formed via covalent or non-covalent assembly of molecules(e.g., macromolecules), such as monomers or polymers. Such polymers ormonomers may be natural or synthetic. Such polymers or monomers may beor include, for example, nucleic acid molecules (e.g., DNA or RNA). Thebead may be formed of a polymeric material. The bead may be magnetic ornon-magnetic. The bead may be rigid. The bead may be flexible and/orcompressible. The bead may be disruptable or dissolvable. The bead maybe a solid particle (e.g., a metal-based particle including but notlimited to iron oxide, gold or silver) covered with a coating comprisingone or more polymers. Such coating may be disruptable or dissolvable.

The term “sample,” as used herein, generally refers to a biologicalsample of a subject. The biological sample may comprise any number ofmacromolecules, for example, cellular macromolecules. The sample may bea cell sample. The sample may be a cell line or cell culture sample. Thesample can include one or more cells. The sample can include one or moremicrobes. The biological sample may be a nucleic acid sample or proteinsample. The biological sample may also be a carbohydrate sample or alipid sample. The biological sample may be derived from another sample.The sample may be a tissue sample, such as a biopsy, core biopsy, needleaspirate, or fine needle aspirate. The sample may be a fluid sample,such as a blood sample, urine sample, or saliva sample. The sample maybe a skin sample. The sample may be a cheek swab. The sample may be aplasma or serum sample. The sample may be a cell-free or cell freesample. A cell-free sample may include extracellular polynucleotides.Extracellular polynucleotides may be isolated from a bodily sample thatmay be selected from the group consisting of blood, plasma, serum,urine, saliva, mucosal excretions, sputum, stool and tears.

The term “biological particle,” as used herein, generally refers to adiscrete biological system derived from a biological sample. Thebiological particle may be a macromolecule. The biological particle maybe a small molecule. The biological particle may be a virus. Thebiological particle may be a cell or derivative of a cell. Thebiological particle may be an organelle. The biological particle may bea rare cell from a population of cells. The biological particle may beany type of cell, including without limitation prokaryotic cells,eukaryotic cells, bacterial, fungal, plant, mammalian, or other animalcell type, mycoplasmas, normal tissue cells, tumor cells, or any othercell type, whether derived from single cell or multicellular organisms.The biological particle may be a constituent of a cell. The biologicalparticle may be or may include DNA, RNA, organelles, proteins, or anycombination thereof. The biological particle may be or may include amatrix (e.g., a gel or polymer matrix) comprising a cell or one or moreconstituents from a cell (e.g., cell bead), such as DNA, RNA,organelles, proteins, or any combination thereof, from the cell. Thebiological particle may be obtained from a tissue of a subject. Thebiological particle may be a hardened cell. Such hardened cell may ormay not include a cell wall or cell membrane. The biological particlemay include one or more constituents of a cell, but may not includeother constituents of the cell. An example of such constituents is anucleus or an organelle. A cell may be a live cell. The live cell may becapable of being cultured, for example, being cultured when enclosed ina gel or polymer matrix, or cultured when comprising a gel or polymermatrix.

The term “macromolecular constituent,” as used herein, generally refersto a macromolecule contained within or from a biological particle. Themacromolecular constituent may comprise a nucleic acid. In some cases,the biological particle may be a macromolecule. The macromolecularconstituent may comprise DNA. The macromolecular constituent maycomprise RNA. The RNA may be coding or non-coding. The RNA may bemessenger RNA (mRNA), ribosomal RNA (rRNA) or transfer RNA (tRNA), forexample. The RNA may be a transcript. The RNA may be small RNA that areless than 200 nucleic acid bases in length, or large RNA that aregreater than 200 nucleic acid bases in length. Small RNAs may include5.8S ribosomal RNA (rRNA), 5S rRNA, transfer RNA (tRNA), microRNA(miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs),Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and smallrDNA-derived RNA (srRNA). The RNA may be double-stranded RNA orsingle-stranded RNA. The RNA may be circular RNA. The macromolecularconstituent may comprise a protein. The macromolecular constituent maycomprise a peptide. The macromolecular constituent may comprise apolypeptide.

The term “molecular tag,” as used herein, generally refers to a moleculecapable of binding to a macromolecular constituent. The molecular tagmay bind to the macromolecular constituent with high affinity. Themolecular tag may bind to the macromolecular constituent with highspecificity. The molecular tag may comprise a nucleotide sequence. Themolecular tag may comprise a nucleic acid sequence. The nucleic acidsequence may be at least a portion or an entirety of the molecular tag.The molecular tag may be a nucleic acid molecule or may be part of anucleic acid molecule. The molecular tag may be an oligonucleotide or apolypeptide. The molecular tag may comprise a DNA aptamer. The moleculartag may be or comprise a primer. The molecular tag may be, or comprise,a protein. The molecular tag may comprise a polypeptide. The moleculartag may be a barcode.

The term “partition,” as used herein, generally, refers to a space orvolume that may be suitable to contain one or more species or conductone or more reactions. A partition may be a physical compartment, suchas a droplet or well. The partition may isolate space or volume fromanother space or volume. The droplet may be a first phase (e.g., aqueousphase) in a second phase (e.g., oil) immiscible with the first phase.The droplet may be a first phase in a second phase that does not phaseseparate from the first phase, such as, for example, a capsule orliposome in an aqueous phase. A partition may comprise one or more other(inner) partitions. In some cases, a partition may be a virtualcompartment that can be defined and identified by an index (e.g.,indexed libraries) across multiple and/or remote physical compartments.For example, a physical compartment may comprise a plurality of virtualcompartments.

The term “chromatin” as used herein generally refers to a complex ofDNA, RNA, and/or proteins that is found in the nucleus of eukaryoticcells. Chromatin may be composed of histone proteins (which formnucleosomes), genomic DNA, DNA binding proteins such as transcriptionfactors, enzymes, and/or epigenetic regulators. The terms “open regionof chromatin” or “accessible region of chromatin” may be usedinterchangeably herein, and generally, but not always, refer to theregions of chromatin between nucleosomes (e.g., unpacked chromatin). Theterms “closed region of chromatin” or “inaccessible region of chromatin”may be used interchangeably herein, and generally, but not always, referto regions of chromatin which include nucleosomes (e.g., packedchromatin).

The term “transcription factor” as used herein generally refers to anyprotein that acts to regulate gene expression levels. In some cases,transcription factors may bind directly to genomic DNA. Non-limitingexamples of transcription factors are provided herein.

The term “histone” as used herein generally refers to proteins found ineukaryotic cells that package and order genomic DNA into structuralunits (e.g., nucleosomes). Non-limiting example of histones are providedherein. The term “histone modification” refers to covalent,post-translational modifications of histone proteins. In some cases,histone modifications may impact gene expression, such as by alteringchromatin structure or by recruiting histone modifiers. Histonemodifications may include methylation, acetylation, phosphorylation,ubiquitylation, and sumoylation. Non-limiting examples of histonemodifications are provided herein.

The term “epigenetic regulator” generally refers to any protein thatregulates or alters chromatin structure. Epigenetic regulators mayinclude, but are not limited to, proteins that add covalentmodifications to histones (e.g., methyl acetyl groups), proteins thatremove covalent modifications from histones, proteins that bind tospecific covalent modifications of histones, and proteins that addcovalent modifications to DNA (e.g., DNA methylation). The term“epigenetic regulator” also encompasses other enzymes that may affectchromatin structure, including, but not limited to, DNA polymerasesand/or RNA polymerases involved in transcription, replication, DNAdamage repair, and the like. Non-limiting examples of epigeneticregulators are provided herein.

Methods of the Disclosure

The disclosure herein provides methods for the detection ofprotein-nucleic acid interactions. In some cases, the disclosureprovides methods for identifying proteins that are bound to or otherwiseinteracting with DNA. In particular, the methods described herein may beused to analyze the interaction of specific proteins with chromatin, andto link this information with a specific genomic location. In somecases, the methods provided herein may be used to identify theinteraction of a transcription factor or an epigenetic regulator with aspecific region of chromatin. In some cases, the methods provided hereinmay be used to identify the interaction of a histone (or a particularhistone modification) with a specific region of chromatin. Generally,the methods provided herein use a proximity-ligation-based approach tophysically link information regarding a specific protein interactionwith a precise genomic location which can be read using traditionalsequencing methods. In some cases, this information may be used todetermine an epigenetic status of a specific chromatin region (e.g.,active transcription site). Advantageously, the methods described hereinmay be used to analyze a plurality of different protein-nucleic acidinteractions simultaneously (e.g., multiplexing). In some cases, themethods may be amenable to analyzing a plurality of differentprotein-nucleic acid interactions in a single cell context.

In one aspect of the disclosure, the methods comprise: a) fragmentingchromatin to generate a plurality of chromatin fragments; b) tagging theplurality of chromatin fragments with a first tag to generate aplurality of first tagged chromatin fragments; c) binding an affinitymolecule to a protein associated with at least one tagged chromatinfragment of the plurality of first tagged chromatin fragments, whereinthe affinity molecule is coupled to a second tag; and d) coupling thefirst tag to the second tag to generate a second tagged chromatinfragment.

In various aspects, chromatin may be fragmented to generate a pluralityof chromatin fragments. Any suitable method of fragmenting chromatin maybe used, including, without limitation, sonication, enzymatic digestion,chemical fragmentation, and the like. In some cases, the fragmentinginvolves fragmenting chromatin at open or accessible regions ofchromatin. In some cases, the fragmenting involves incubating chromatinwith an enzyme that preferentially fragments chromatin at open oraccessible regions (e.g., a hyperactive Tn5 transposase).

In various aspects, chromatin may be isolated prior to fragmenting.Chromatin may be isolated by any suitable method. In some cases, cellnuclei may be isolated and lysed, thereby releasing chromatin from thenuclear envelope. The isolated chromatin may then be fragmentedaccording to methods described herein. In other cases, fragmenting maybe performed directly inside an intact cell nucleus. In a non-limitingexample, cell nuclei may be isolated and permeabilized (or intact cellsmay be isolated and permeabilized), allowing a transposase enzyme toaccess the chromatin inside the cell nucleus. Cell nuclei may bepermeabilized by any suitable method, including, but not limited to,treatment with a permeabilization agent (e.g., digitonin, NP40,Tween-20, saponin, etc.) or by sonication. Preferentially, cells or cellnuclei are not fixed prior to fragmenting. For example, the methodsdescribed herein do not require chromatin to be cross-linked (e.g., bytreatment with a fixative agent). In some cases, chromatin is notdiluted prior to fragmenting. For example, the methods described hereinprovide for fragmenting chromatin without prior dilution (e.g., toremove permeabilization reagents, etc.). In some cases, a single cell ora single nucleus may be isolated from a population of cells prior tofragmenting, such that chromatin from a single cell may be analyzed.

In various aspects, fragmenting chromatin according to the methodsprovided herein generates a plurality of chromatin fragments. Eachchromatin fragment of the plurality of chromatin fragments maycorrespond to a different region of chromatin. Each chromatin fragmentof the plurality of chromatin fragments may include genomic DNA, RNA,and/or proteins associated with the genomic DNA. In some cases, the oneor more proteins may include one or more transcription factors, histones(including histone modifications), epigenetic regulators, or anycombination thereof. In situations in which a single cell is isolatedfrom a population of cells prior to fragmenting, each chromatin fragmentmay correspond to a different chromatin region from the single cell.

In various aspects, the methods further involve tagging the plurality ofchromatin fragments with a first tag to generate a plurality of firsttagged chromatin fragments. In some cases, the first tag is a universaltag, such that each of the plurality of first tagged chromatin fragmentscontains the same tag. The first tag may be any suitable type ofmolecular tag, such as, but not limited to, a protein, a peptide, anantibody, an aptamer, a fluorophore, a hapten, an oligonucleotide, anucleotide modification, and the like. In particular aspects, the firsttag is an oligonucleotide tag. In some cases, the oligonucleotide tag isa double-stranded oligonucleotide. In some cases, the double-strandedoligonucleotide comprises a single-stranded overhang. In some cases, theoligonucleotide tag is a universal DNA adapter, such as a sequencingadapter. Any sequencing adapter may be used and may be selected based ona desired downstream sequencing platform. Tagging may be accomplished byany suitable means, including, without limitation, ligation,hybridization, and the like. The first tag may be attached to a 5′ end,a 3′ end, or both, of the chromatin fragment. In some cases, the firsttag may comprise additional features such as one or more sequencingadapters, sample barcodes, and the like.

In some cases, both the fragmenting and the tagging may be performedsimultaneously. In a particular example, the fragmenting and the taggingmay involve a tagmentation reaction. The term “tagmentation reaction” isused herein to refer to the simultaneous cleaving and tagging of anucleic acid molecule (typically by use of an enzyme). In some cases,the tagmentation reaction is performed by a transposase enzyme. Thetransposase enzyme may be loaded with a first tag. In some cases, thefirst tag comprises a transposon end sequence. In particular examples,the transposon end sequence may be a Mosaic End (ME) sequence. The firsttag may further comprise a suitable sequencing adapter, which may beselected based on a desired downstream sequencing platform. In anon-limiting example, the first tag may comprise a R2 universal adapter(e.g., for use with Illumina sequencing systems). Upon incubation withchromatin, the transposase may simultaneously cleave the chromatin andattach the first tag to an end of the chromatin fragment, therebygenerating a first tagged chromatin fragment. In some cases, thetransposase may preferentially cleave the chromatin at open oraccessible regions. Non-limiting examples of transposases that may beused in a tagmentation reaction include: a Tn transposase (e.g., Tn3,Tn5, Tn7, Tn10, Tn552, Tn903), a MuA tranposase, a Vibhar transposase(e.g., from Vibrio harveyi), a prokaryotic transposase, any member ofthe hAT superfamily of transposases (e.g., Hermes), Ac-Ds, Ascot-1, Bs1,Cin4, Copia, En/Spm, F element, hobo, Hsmarl, Hsmar2, IN (HIV), IS1,IS2, IS3, IS4, ISS, IS6, IS10, IS21, IS30, IS50, IS51, IS150, IS256,IS407, IS427, IS630, IS903, IS911, IS982, IS1031, ISL2, L1, Mariner, Pelement, Tam3, Tc1, Tc3, Te1, THE-1, Tn/O, TnA, To11, To12, Tn10, andTy1. In some cases, the transposase may be derived from any of theabove, such as a transposase including one or more mutations ormodifications. In a particular aspect, the transposase is a hyperactiveTn5 transposase.

In some cases, chromatin may be isolated prior to performing atagmentation reaction. Chromatin may be isolated by any suitable method.In some cases, cell nuclei may be isolated and lysed, thereby releasingchromatin from the nuclear envelope. The isolated chromatin may then betagmented according to methods described herein. In other cases, atagmentation reaction may be performed directly inside an intact cellnucleus. In a non-limiting example, cell nuclei may be isolated andpermeabilized, allowing a transposase enzyme (containing the first tag)to access the chromatin inside the cell nucleus. Cell nuclei may bepermeabilized by any suitable method, including, but not limited to,treatment with a permeabilization agent (e.g., digitonin, NP40,Tween-20, saponin, etc.) or by sonication. Preferentially, cells or cellnuclei are not fixed prior to performing the tagmentation reaction. Forexample, the methods described herein do not require chromatin to becross-linked (e.g., by treatment with a fixative agent) prior toperforming the tagmentation reaction. In some cases, chromatin is notdiluted prior to performing the tagmentation reaction. For example, themethods described herein provide for performing the tagmentationreaction without prior dilution (e.g., to remove permeabilizationreagents, etc.). In some cases, a single cell or a single nucleus may beisolated from a population of cells prior to performing the tagmentationreaction, such that chromatin from a single cell may be analyzed.

In various aspects, the methods further involve binding an affinitymolecule to a protein associated with at least one of the first taggedchromatin fragments. In some cases, the affinity molecule mayselectively bind to a transcription factor. Non-limiting examples oftranscription factors are described herein. In some cases, the affinitymolecule may selectively bind to a histone. Non-limiting examples ofhistones are described herein. In some cases, the affinity molecule mayselectively bind to a histone modification (e.g., a covalent,post-translational modification of a histone). Non-limiting examples ofhistone modifications are described herein. In some cases, the affinitymolecule may selectively bind to an epigenetic regulator. Non-limitingexamples of epigenetic regulators are described herein. The affinitymolecule may be any type of molecule that is capable of selectivelybinding to a protein associated with the chromatin fragments.Non-limiting examples of affinity molecules include: antibodies andfragments thereof, aptamers, proteins, peptides, small molecules,oligonucleotides, and the like. In particular examples, the affinitymolecule is an antibody or antibody fragment. In some cases, a pluralityof affinity molecules may be used, e.g., a plurality of differentantibodies or antibody fragments, each capable of selectively binding todifferent proteins associated with the chromatin fragments. In somecases, the affinity molecule may be a protein or peptide. Non-limitingexamples of protein or peptides that may be used as affinity moleculesmay include chromatin organization modifier domains (chromodomains), orproteins or peptides that include chromodomains; or bromodomains, orproteins or peptides that include bromodomains (e.g., BRD2, BRD3, BRD4,BRD7, BRD9, BRDT, ASHL1, EP300, PCAF).

In various aspects, the affinity molecule may be coupled to a secondtag. The second tag may be any suitable type of molecular tag, such as,but not limited to, a protein, a peptide, an antibody, an aptamer, afluorophore, a hapten, an oligonucleotide, a nucleotide modification,and the like. In particular aspects, the second tag may be anoligonucleotide tag. In some cases, the oligonucleotide tag is adouble-stranded oligonucleotide. In some cases, the double-strandedoligonucleotide tag may comprise a single-stranded overhang. In somecases, the single-stranded overhang of the second tag may becomplementary to a single-stranded overhang of a differentoligonucleotide (such as the first tag).

In various aspects, the second tag may comprise an affinity moleculebarcode. The affinity molecule barcode may act as a label for aparticular type of affinity molecule. For example, an affinity molecule(A) that selectively binds to a protein (X) may be coupled to a secondtag comprising a barcode that corresponds to affinity molecule (A).Similarly, an affinity molecule (B) that selectively binds to a protein(Y) may be coupled to a second tag comprising a barcode that correspondsto affinity molecule (B). Preferentially, each different affinitymolecule (or type thereof) may be coupled to a second tag that comprisesan affinity molecule barcode unique for each different affinity molecule(or type thereof). In such cases, a plurality of different types ofaffinity molecules, each coupled to a unique affinity molecule barcode,and each capable of binding to a different type of protein associatedwith the chromatin fragments, may be used. The identity of the proteinmay then be indirectly ascertained by identifying the affinity moleculebarcode in a downstream process (e.g., by sequencing). Labeling eachaffinity molecule with a different affinity molecule barcode providesfor the analysis of multiple different protein-nucleic acid interactionsin the same sample.

In various aspects, the second tag may comprise, in addition to anaffinity molecule barcode, one or more suitable features. For example,the second tag may comprise one or more sequencing adapters suitable fora desired downstream sequencing platform (e.g., P7 for Illumina-basedsequencers), or additional barcodes or tags.

In various aspects, the method further involves coupling the first tagto the second tag to generate a second tagged chromatin fragment. Insome cases, the first tag and the second tag are both double-strandedoligonucleotide tags. In some cases, the first oligonucleotide tag maycomprise a single-stranded overhang that is complementary to asingle-stranded overhang of the second oligonucleotide tag. In suchcases, the complementary single-stranded overhang of the firstoligonucleotide tag and the second oligonucleotide tag may be annealedand ligated (e.g., by proximity ligation), thereby coupling the firstand second oligonucleotide tags. By coupling the first and second tagsin this way, second tagged chromatin fragments are generated. The secondtagged chromatin fragments may contain genomic DNA sequence thatcorresponds to the location at which the protein analyte is bound to theDNA. The second tagged chromatin fragments may further comprise thefirst tag which may be used to ascertain the precise location ofchromatin fragmentation (e.g., by determining where the transposon endsequence has been inserted). The second tagged chromatin fragments mayfurther comprise the second tag which may be used to identify theprotein that was bound to the genomic DNA at the location be analyzed(e.g., by identifying the affinity molecule barcode).

In alternative embodiments, a first oligonucleotide tag and a secondoligonucleotide tag may be coupled by use of a third oligonucleotide tag(also referred to herein as a bridging oligonucleotide). In some cases,the first, second, and third oligonucleotide tags are double-stranded.In some cases, the third oligonucleotide tag (or bridgingoligonucleotide) may comprise a single-stranded overhang at a first endthat is complementary to the single-stranded overhang of the firstoligonucleotide tag, and may further comprise a single-stranded overhangat a second end that is complementary to the single-stranded overhang ofthe second oligonucleotide tag. The third oligonucleotide tag (orbridging oligonucleotide) may be annealed and ligated to thesingle-stranded overhang of the first oligonucleotide tag and to thesingle-stranded overhang of the second oligonucleotide tag, therebycoupling the first, second, and third oligonucleotide tags to generatethe second tagged chromatin fragments. In such cases, the second taggedchromatin fragments may contain genomic DNA sequence that corresponds tothe location at which the protein analyte is bound to the DNA. Thesecond tagged chromatin fragments may further comprise the first tagwhich may be used to ascertain the precise location of chromatinfragmentation (e.g., by determining where the transposon end sequencehas been inserted). The second tagged chromatin fragments may furthercomprise the second tag which may be used to identify the protein thatwas bound to the genomic DNA at the location be analyzed (e.g., byidentifying the affinity molecule barcode). The second tagged chromatinfragments may further comprise the third tag which may be used toidentify the cell source of the chromatin (e.g., by identifying the cellbarcode) or to identify a unique chromatin fragment (e.g., byidentifying the UMI). In some cases, the first and second tags may becoupled by a plurality of bridging tags (e.g., bridging oligonucleotidemolecules). In some cases, the plurality of bridging tags may bepre-coupled as one or more structures before coupling to the first andsecond tags.

In a non-limiting aspect, the fragmenting and tagging (or thetagmentation reaction) may occur in a partition. For example, aplurality of cells or cell nuclei may be partitioned into a plurality ofpartitions, such that each one of the plurality of the partitionscontains no more than a single cell or a single cell nucleus. In oneexample, the single cell or single cell nucleus may be lysed in apartition, and then the chromatin may be fragmented and tagged inaccordance with the methods provided herein. In another example, thesingle cell or single cell nucleus may be permeabilized (either prior topartitioning, or after partitioning) and then the chromatin may befragmented and tagged inside the cell nucleus in accordance with themethods provided herein. In various aspects, a plurality of affinitymolecules, each capable of selectively binding to different proteins ofinterest, may be introduced into the partition, and allowed to bind toeach respective protein.

In another non-limiting aspect, cells or cell nuclei may be lysed orpermeabilized prior to partitioning. In some cases, a plurality of cellsor cell nuclei may be isolated from a cell source. In other cases,individual cells or cell nuclei may be isolated prior to lysis orpermeabilization. The cells or cell nuclei may be lysed or permeabilizedin accordance with the methods provided herein. In some cases, aplurality of affinity molecules, each capable of selectively binding todifferent proteins or peptides of interest, may be bound to eachrespective protein or peptide prior to partitioning. In one example, thetagging and fragmenting may also occur prior to partitioning. In thisexample, the tagged chromatin fragments with a plurality of affinitymolecules bound thereto may then be partitioned into one or morepartitions. In another example, intact chromatin with a plurality ofaffinity molecules bound thereto may be partitioned into one or morepartitions, and then the tagging and fragmenting may occur within apartition.

The partition may be a droplet emulsion or a well. In some cases, eachpartition may contain first tagged chromatin fragments from a singlecell. Each partition may further comprise a single particle coated witha plurality of third oligonucleotide tags. In some cases, the particlemay be a bead (e.g., a gel bead). Each of the third oligonucleotide tagsmay be attached to the surface of the bead. In some cases, each of thethird oligonucleotide tags are releasably attached to the surface of thebead. Each of the third oligonucleotide tags on a single particle maycomprise a cell barcode. A cell barcode may be a nucleic acid sequencethat, when sequenced and identified, provides information as to the cellsource of the analyte. Each cell barcode coupled to a single particlemay be the same cell barcode, such that, when the third oligonucleotidetag is coupled to the first and second oligonucleotide tags, the cellbarcode labels each resulting second tagged chromatin fragment as beingfrom the same single cell. Each of the third oligonucleotide tags on asingle particle may further comprise a unique molecular identifier(UMI). Each UMI coupled to a single particle may be different, suchthat, when the third oligonucleotide tag is coupled to the first andsecond oligonucleotide tags, the UMI labels each resulting second taggedchromatin fragment as a unique molecule. The third oligonucleotide tagmay further comprise one or more additional adapters, tags, barcodes,and the like. For example, the third oligonucleotide tag may furthercomprise a sequencing adapter.

In various aspects, the methods further provide for additionaldownstream processing of the second tagged chromatin fragments. In somecases, the second tagged chromatin fragments may be used to generate alibrary for downstream sequencing processes. In some cases, the secondtagged chromatin fragments may serve as a template for a second strandsynthesis reaction. For example, a primer may be annealed to acomplementary sequence on the second tagged chromatin fragments and thereverse complementary sequence may be synthesized in the presence of aDNA polymerase. The primer may contain additional adapters or barcodessuitable for use in a sequencing reaction. In some cases, the secondtagged chromatin fragments may be amplified to generate a plurality ofamplified fragments. In some cases, the second tagged chromatinfragments or a library derived therefrom may be used in a sequencingreaction. Any suitable sequencing platform may be used, and variousexamples are described herein. In various aspects, sequencing adapterssuitable for use in a particular sequencing platform may be coupled tothe second tagged chromatin fragments. For example, sequencing adaptersmay be included in one or more of the first tag, the second tag, or thethird tag.

FIGS. 10-12 depict non-limiting examples of the methods describedherein. As shown in FIGS. 10-12, cells or cell nuclei may be lysed ormay be permeabilized and chromatin contained therein may be contactedwith: (1) a transposase-nucleic acid complex comprising a universal setof nucleic acid transposase adapters (e.g., 1002 comprising a sequencingprimer sequence (R2) and a transposon end sequence (ME)); and (2)antibodies labeled with distinct nucleic acid sequences (e.g., 1001) totheir target proteins (see, e.g., 1101). The nucleic acid antibodyadapter molecules attached to each antibody (e.g., 1001) may comprise anantibody barcode sequence (aB) that functions to identify the protein towhich the antibody is specific. Additional functional sequences (such asa R1 sequencing primer or a P7 adapter sequence) can also be included inthe antibody adapters. The use of unique antibody barcode sequencesattached to each antibody allows the probing and identification ofmultiple different protein targets at the same time.

The adapter-flanked (e.g., 1002) template genomic DNA fragments and theantibody adapter molecule (e.g., 1001) may then be physically linked,either directly or using a bridging oligonucleotide (e.g., 1003)containing unique identifiers, such as a cell barcode (CB) and/or aunique molecular identifier (UMI). For example, in some cases, followingtransposition and antibody incubation, cell nuclei (or cells) may bepartitioned (e.g., in a droplet emulsion) such that each partitioncomprises a single nucleus (or a single cell) and a plurality of linkermolecules (also referred to as a bridging oligonucleotide). In someembodiments, the linker molecules may be attached to a bead, such as agel bead. In some instances, the linker molecules may be releasablyattached to the bead as described elsewhere herein. Using thecomplementary overhang sequences of the transposase adapter 1002 and theantibody adapter 1001, the bridging oligonucleotide 1003 may connect(e.g., by ligation) the fragments together (e.g., 1102).

The assembled fragments (e.g., 1102) can then be recovered (includingdenaturation to make single stranded) and second strand synthesis (see,e.g., 1103) can be performed using a random primer containing the R1 andME sequences (e.g., 1004). In some instances, to complete librarypreparation, additional sequences (such as P5, i5, or i7) can be addedto the fragments (either by inclusion in the oligonucleotides describedin FIG. 10 or by addition by one or more reactions, such as PCR). Duringsequencing, Read1 provides information about the genomic location,however, the precise position of the transposition is lost due to randompriming of the template genomic DNA fragment. Read2 provides the preciseinsertion of the actual transposition event. i7 provides the antibodybarcode, UMI and cell barcode and i5 contains the sample barcodes, whichare added during the downstream transposition.

Under an alternative configuration as shown in FIG. 12, the Readlsequence is moved to read the cell barcode (CB), UMI, and antibodybarcode (aB), while Read2 provides the genomic location of the proteinbinding site based on the transposition event. Here the H7 and H5handles allow the sample indices to be added during one or moresubsequent reactions (such as PCR).

Advantageously, the methods described herein provide for thesimultaneous detection of multiple protein-nucleic acid interactions ina single cell. In a non-limiting example, a plurality of affinitymolecules, each capable of selectively binding to a protein associatedwith a region of chromatin, may be used. Because each affinity moleculecontains a different affinity molecule barcode, multiple proteins may beanalyzed in the same sample at the same time. In some cases, the methodsprovided herein allow for the simultaneous detection of 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,85, 90, 95, 100, or greater than 100 protein-nucleic acid interactions.

In various aspects, the methods may be used to analyze the interactionof one or more transcription factors with a region of chromatin.Non-limiting examples of transcription factors that may be analyzedusing the methods described herein include: AC008770.3, AC023509.3,AC092835.1, AC138696.1, ADNP, ADNP2, AEBP1, AEBP2, AHCTF1, AHDC1, AHR,AHRR, AIRE, AKAP8, AKAP8L, AKNA, ALX1, ALX3, ALX4, ANHX, ANKZF1, AR,ARGFX, ARHGAP35, ARID2, ARID3A, ARID3B, ARID3C, ARID5A, ARID5B, ARNT,ARNT2, ARNTL, ARNTL2, ARX, ASCL1, ASCL2, ASCL3, ASCL4, ASCL5, ASH1L,ATF1, ATF2, ATF3, ATF4, ATF5, ATF6, ATF6B, ATF7, ATMIN, ATOH1, ATOH7,ATOH8, BACH1, BACH2, BARHL1, BARHL2, BARX1, BARX2, BATF, BATF2, BATF3,BAZ2A, BAZ2B, BBX, BCL11A, BCL11B, BCL6, BCL6B, BHLHA15, BHLHA9,BHLHE22, BHLHE23, BHLHE40, BHLHE41, BNC1, BNC2, BORCS8-MEF2B, BPTF,BRF2, BSX, C11orf95, CAMTA1, CAMTA2, CARF, CASZ1, CBX2, CC2D1A,CCDC169-SOHLH2, CCDC17, CDC5L, CDX1, CDX2, CDX4, CEBPA, CEBPB, CEBPD,CEBPE, CEBPG, CEBPZ, CENPA, CENPB, CENPBD1, CENPS, CENPT, CENPX, CGGBP1,CHAMP1, CHCHD3, CIC, CLOCK, CPEB1, CPXCR1, CREB1, CREB3, CREB3L1,CREB3L2, CREB3L3, CREB3L4, CREB5, CREBL2, CREBZF, CREM, CRX, CSRNP1,CSRNP2, CSRNP3, CTCF, CTCFL, CUX1, CUX2, CXXC1, CXXC4, CXXC5, DACH1,DACH2, DBP, DBX1, DBX2, DDIT3, DEAF1, DLX1, DLX2, DLX3, DLX4, DLX5,DLX6, DMBX1, DMRT1, DMRT2, DMRT3, DMRTA1, DMRTA2, DMRTB1, DMRTC2, DMTF1,DNMT1, DNTTIP1, DOT1L, DPF1, DPF3, DPRX, DR1, DRAP1, DRGX, DUX1, DUX3,DUX4, DUXA, DZIP1, E2F1, E2F2, E2F3, E2F4, E2F5, E2F6, E2F7, E2F8, E4F1,EBF1, EBF2, EBF3, EBF4, EEA1, EGR1, EGR2, EGR3, EGR4, EHF, ELF1, ELF2,ELF3, ELF4, ELF5, ELK1, ELK3, ELK4, EMX1, EMX2, EN1, EN2, EOMES, EPAS1,ERF, ERG, ESR1, ESR2, ESRRA, ESRRB, ESRRG, ESX1, ETS1, ETS2, ETV1, ETV2,ETV3, ETV3L, ETV4, ETV5, ETV6, ETV7, EVX1, EVX2, FAM170A, FAM200B,FBXL19, FERD3L, FEV, FEZF1, FEZF2, FIGLA, FIZ1, FLI1, FLYWCH1, FOS,FOSB, FOSL1, FOSL2, FOXA1, FOXA2, FOXA3, FOXB1, FOXB2, FOXC1, FOXC2,FOXD1, FOXD2, FOXD3, FOXD4, FOXD4L1, FOXD4L3, FOXD4L4, FOXD4L5, FOXD4L6,FOXE1, FOXE3, FOXF1, FOXF2, FOXG1, FOXH1, FOXI1, FOXI2, FOXI3, FOXJ1,FOXJ2, FOXJ3, FOXK1, FOXK2, FOXL1, FOXL2, FOXM1, FOXN1, FOXN2, FOXN3,FOXN4, FOXO1, FOXO3, FOXO4, FOXO6, FOXP1, FOXP2, FOXP3, FOXP4, FOXQ1,FOXR1, FOXR2, FOXS1, GABPA, GATA1, GATA2, GATA3, GATA4, GATA5, GATA6,GATAD2A, GATAD2B, GBX1, GBX2, GCM1, GCM2, GFI1, GFI1B, GLI1, GLI2, GLI3,GLI4, GLIS1, GLIS2, GLIS3, GLMP, GLYR1, GMEB1, GMEB2, GPBP1, GPBP1L1,GRHL1, GRHL2, GRHL3, GSC, GSC2, GSX1, GSX2, GTF2B, GTF2I, GTF2IRD1,GTF2IRD2, GTF2IRD2B, GTF3A, GZF1, HAND1, HAND2, HBP1, HDX, HELT, HES1,HES2, HES3, HES4, HESS, HES6, HEST, HESX1, HEY1, HEY2, HEYL, HHEX, HIC1,HIC2, HIF1A, HIF3A, HINFP, HIVEP1, HIVEP2, HIVEP3, HKR1 , HLF, HLX,HMBOX1, HMG20A, HMG20B, HMGA1, HMGA2, HMGN3, HMX1, HMX2, HMX3, HNF1A,HNF1B, HNF4A, HNF4G, HOMEZ, HOXA1, HOXA10, HOXA11, HOXA13, HOXA2, HOXA3,HOXA4, HOXA5, HOXA6, HOXA7, HOXA9, HOXB1, HOXB13, HOXB2, HOXB3, HOXB4,HOXB5, HOXB6, HOXB7, HOXB8, HOXB9, HOXC10, HOXC11, HOXC12, HOXC13,HOXC4, HOXC5, HOXC6, HOXC8, HOXC9, HOXD1, HOXD10, HOXD11, HOXD12,HOXD13, HOXD3, HOXD4, HOXD8, HOXD9, HSF1, HSF2, HSF4, HSF5, HSFX1,HSFX2, HSFY1 HSFY2, IKZF1, IKZF2, IKZF3, IKZF4, IKZF5, INSM1, INSM2,IRF1, IRF2, IRF3, IRF4, IRF5, IRF6, IRF7, IRF8, IRF9, IRX1, IRX2, IRX3,IRX4, IRX5, IRX6, ISL1, ISL2, ISX, JAZF1, JDP2, JRK, JRKL, JUN, JUNB,JUND, KAT7, KCMF1, KCNIP3, KDM2A, KDM2B, KDM5B, KIN, KLF1, KLF10, KLF11,KLF12, KLF13, KLF14, KLF15, KLF16, KLF17, KLF2, KLF3, KLF4, KLF5, KLF6,KLF7, KLF8, KLF9, KMT2A, KMT2B, L3MBTL1, L3MBTL3, L3MBTL4, LBX1, LBX2,LCOR, LCORL, LEF1, LEUTX, LHX1, LHX2, LHX3, LHX4, LHX5, LHX6, LHX8,LHX9, LIN28A, LIN28B, LIN54, LMX1A, LMX1B, LTF, LYL1, MAF, MAFA, MAFB,MAFF, MAFG, MAFK, MAX, MAZ, MBD1, MBD2, MBD3, MBD4, MBD6, MBNL2, MECOM,MECP2, MEF2A, MEF2B, MEF2C, MEF2D, MEIS1, MEIS2, MEIS3, MEOX1, MEOX2,MESP1, MESP2, MGA, MITF, MIXL1, MKX, MLX, MLXIP, MLXIPL, MNT, MNX1,MSANTD1, MSANTD3, MSANTD4, MSC, MSGN1, MSX1, MSX2, MTERF1, MTERF2,MTERF3, MTERF4, MTF1, MTF2, MXD1, MXD3, MXD4, MXI1, MYB, MYBL1, MYBL2,MYC, MYCL, MYCN, MYF5, MYF6, MYNN, MYOD1, MYOG, MYPOP, MYRF, MYRFL,MYSM1, MYT1, MYT1L, MZF1, NACC2, NAIF1, NANOG, NANOGNB, NANOGP8, NCOA1,NCOA2, NCOA3, NEUROD1, NEUROD2, NEUROD4, NEUROD6, NEUROG1, NEUROG2,NEUROG3, NFAT5, NFATC1, NFATC2, NFATC3, NFATC4, NFE2, NFE2L1, NFE2L2,NFE2L3, NFE4, NFIA, NFIB, NFIC, NFIL3, NFIX, NFKB1, NFKB2, NFX1, NFXL1,NFYA, NFYB, NFYC, NHLH1, NHLH2, NKRF, NKX1-1, NKX1-2, NKX2-1, NKX2-2,NKX2-3, NKX2-4, NKX2-5, NKX2-6, NKX2-8, NKX3-1, NKX3-2, NKX6-1, NKX6-2,NKX6-3, NME2, NOBOX, NOTO, NPAS1, NPAS2, NPAS3, NPAS4, NROB1, NR1D1,NR1D2, NR1H2, NR1H3, NR1H4, NR1I2, NR1I3, NR2C1, NR2C2, NR2E1, NR2E3,NR2F1, NR2F2, NR2F6, NR3C1, NR3C2, NR4A1, NR4A2, NR4A3, NR5A1, NR5A2,NR6A1, NRF1, NRL, OLIG1, OLIG2, OLIG3, ONECUT1, ONECUT2, ONECUT3, OSR1,OSR2, OTP, OTX1, OTX2, OVOL1, OVOL2, OVOL3, PA2G4, PATZ1, PAX1, PAX2,PAX3, PAX4, PAX5, PAX6, PAX7, PAX8, PAX9, PBX1, PBX2, PBX3, PBX4, PCGF2,PCGF6, PDX1, PEG3, PGR, PHF1, PHF19, PHF20, PHF21A, PHOX2A, PHOX2B,PIN1, PITX1, PITX2, PITX3, PKNOX1, PKNOX2, PLAG1, PLAGL1, PLAGL2,PLSCR1, POGK, POU1F1, POU2AF1, POU2F1, POU2F2, POU2F3, POU3F1, POU3F2,POU3F3, POU3F4, POU4F1, POU4F2, POU4F3, POU5F1, POU5F1B, POU5F2, POU6F1,POU6F2, PPARA, PPARD, PPARG, PRDM1, PRDM10, PRDM12, PRDM13, PRDM14,PRDM15, PRDM16, PRDM2, PRDM4, PRDM5, PRDM6, PRDM8, PRDM9, PREB, PRMT3,PROP1, PROX1, PROX2, PRR12, PRRX1, PRRX2, PTF1A, PURA, PURB, PURG, RAG1,RARA, BARB, RARG, RAX, RAX2, RBAK, RBCK1, RBPJ, RBPJL, RBSN, REL, RELA,RELB, REPIN1, REST, REXO4, RFX1, RFX2, RFX3, RFX4, RFX5, RFX6, RFX7,RFX8, RHOXF1, RHOXF2, RHOXF2B, RLF, RORA, RORB, RORC, RREB1, RUNX1,RUNX2, RUNX3, RXRA, RXRB, RXRG, SAFB, SAFB2, SALL1, SALL2, SALL3, SALL4,SATB1, SATB2, SCMH1, SCML4, SCRT1, SCRT2, SCX, SEBOX, SETBP1, SETDB1,SETDB2, SGSM2, SHOX, SHOX2, SIM1, SIM2, SIX1, SIX2, SIX3, SIX4, SIX5,SIX6, SKI, SKIL, SKOR1, SKOR2, SLC2A4RG, SMAD1, SMAD3, SMAD4, SMAD5,SMAD9, SMYD3, SNAI1, SNAI2, SNAI3, SNAPC2, SNAPC4, SNAPC5, SOHLH1,SOHLH2, SON, SOX1, SOX10, SOX11, SOX12, SOX13, SOX14, SOX15, SOX17,SOX18, SOX2, SOX21, SOX3, SOX30, SOX4, SOX5, SOX6, SOX7, SOX8, SOX9,SP1, SP100, SP110, SP140, SP140L, SP2, SP3, SP4, SPS, SP6, SP7, SP8,SP9, SPDEF, SPEN, SPI1, SPIB, SPIC, SPZ1, SRCAP, SREBF1, SREBF2, SRF,SRY, ST18, STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, STAT6, TAL1,TAL2, TBP, TBPL1, TBPL2, TBR1, TBX1, TBX10, TBX15, TBX18, TBX19, TBX2,TBX20, TBX21, TBX22, TBX3, TBX4, TBX5, TBX6, TCF12, TCF15, TCF20, TCF21,TCF23, TCF24, TCF3, TCF4, TCF7, TCF7L1, TCF7L2, TCFL5, TEAD1, TEAD2,TEAD3, TEAD4, TEF, TERB1, TERF1, TERF2, TET1, TET2, TET3, TFAP2A,TFAP2B, TFAP2C, TFAP2D, TFAP2E, TFAP4, TFCP2, TFCP2L1, TFDP1, TFDP2,TFDP3, TFE3, TFEB, TFEC, TGIF1, TGIF2, TGIF2LX, TGIF2LY, THAP1, THAP10,THAP11, THAP12, THAP2, THAP3, THAP4, THAP5, THAP6, THAP7, THAP8, THAP9,THRA, THRB, THYN1, TIGD1, TIGD2, TIGD3, TIGD4, TIGD5, TIGD6, TIGD7,TLX1, TLX2, TLX3, TMF1, TOPORS, TP53, TP63, TP73, TPRX1, TRAFD1, TRERF1,TRPS1, TSC22D1, TSHZ1, TSHZ2, TSHZ3, TTF1, TWIST1, TWIST2, UBP1, UNCX,USF1, USF2, USF3, VAX1, VAX2, VDR, VENTX, VEZF1, VSX1, VSX2, WIZ, WT1,XBP1, XPA, YBX1, YBX2, YBX3, YY1, YY2, ZBED1, ZBED2, ZBED3, ZBED4,ZBED5, ZBED6, ZBED9, ZBTB1, ZBTB10, ZBTB11, ZBTB12, ZBTB14, ZBTB16,ZBTB17, ZBTB18, ZBTB2, ZBTB20, ZBTB21, ZBTB22, ZBTB24, ZBTB25, ZBTB26,ZBTB3, ZBTB32, ZBTB33, ZBTB34, ZBTB37, ZBTB38, ZBTB39, ZBTB4, ZBTB40,ZBTB41, ZBTB42, ZBTB43, ZBTB44, ZBTB45, ZBTB46, ZBTB47, ZBTB48, ZBTB49,ZBTB5, ZBTB6, ZBTB7A, ZBTB7B, ZBTB7C, ZBTB8A, ZBTB8B, ZBTB9, ZC3H8,ZEB1, ZEB2, ZFAT, ZFHX2, ZFHX3, ZFHX4, ZFP1, ZFP14, ZFP2, ZFP28, ZFP3,ZFP30, ZFP37, ZFP41, ZFP42, ZFP57, ZFP62, ZFP64, ZFP69, ZFP69B, ZFP82,ZFP90, ZFP91, ZFP92, ZFPM1, ZFPM2, ZFX, ZFY, ZGLP1, ZGPAT, ZHX1, ZHX2,ZHX3, ZIC1, ZIC2, ZIC3, ZIC4, ZIC5, ZIK1, ZIM2, ZIM3, ZKSCAN1, ZKSCAN2,ZKSCAN3, ZKSCAN4, ZKSCAN5, ZKSCAN7, ZKSCAN8, ZMAT1, ZMAT4, ZNF10,ZNF100, ZNF101, ZNF107, ZNF112, ZNF114, ZNF117, ZNF12, ZNF121, ZNF124,ZNF131, ZNF132, ZNF133, ZNF134, ZNF135, ZNF136, ZNF138, ZNF14, ZNF140,ZNF141, ZNF142, ZNF143, ZNF146, ZNF148, ZNF154, ZNF155, ZNF157, ZNF16,ZNF160, ZNF165, ZNF169, ZNF17, ZNF174, ZNF175, ZNF177, ZNF18, ZNF180,ZNF181, ZNF182, ZNF184, ZNF189, ZNF19, ZNF195, ZNF197, ZNF2, ZNF20,ZNF200, ZNF202, ZNF205, ZNF207, ZNF208, ZNF211, ZNF212, ZNF213, ZNF214,ZNF215, ZNF217, ZNF219, ZNF22, ZNF221, ZNF222, ZNF223, ZNF224, ZNF225,ZNF226, ZNF227, ZNF229, ZNF23, ZNF230, ZNF232, ZNF233, ZNF234, ZNF235,ZNF236, ZNF239, ZNF24, ZNF248, ZNF25, ZNF250, ZNF251, ZNF253, ZNF254,ZNF256, ZNF257, ZNF26, ZNF260, ZNF263, ZNF264, ZNF266, ZNF267, ZNF268,ZNF273, ZNF274, ZNF275, ZNF276, ZNF277, ZNF28, ZNF280A, ZNF280B,ZNF280C, ZNF280D, ZNF281, ZNF282, ZNF283, ZNF284, ZNF285, ZNF286A,ZNF286B, ZNF287, ZNF292, ZNF296, ZNF3, ZNF30, ZNF300, ZNF302, ZNF304,ZNF311, ZNF316, ZNF317, ZNF318, ZNF319, ZNF32, ZNF320, ZNF322, ZNF324,ZNF324B, ZNF326, ZNF329, ZNF331, ZNF333, ZNF334, ZNF335, ZNF337, ZNF33A,ZNF33B, ZNF34, ZNF341, ZNF343, ZNF345, ZNF346, ZNF347, ZNF35, ZNF350,ZNF354A, ZNF354B, ZNF354C, ZNF358, ZNF362, ZNF365, ZNF366, ZNF367,ZNF37A, ZNF382, ZNF383, ZNF384, ZNF385A, ZNF385B, ZNF385C, ZNF385D,ZNF391, ZNF394, ZNF395, ZNF396, ZNF397, ZNF398, ZNF404, ZNF407, ZNF408,ZNF41, ZNF410, ZNF414, ZNF415, ZNF416, ZNF417, ZNF418, ZNF419, ZNF420,ZNF423, ZNF425, ZNF426, ZNF428, ZNF429, ZNF43, ZNF430, ZNF431, ZNF432,ZNF433, ZNF436, ZNF438, ZNF439, ZNF44, ZNF440, ZNF441, ZNF442, ZNF443,ZNF444, ZNF445, ZNF446, ZNF449, ZNF45, ZNF451, ZNF454, ZNF460, ZNF461,ZNF462, ZNF467, ZNF468, ZNF469, ZNF470, ZNF471, ZNF473, ZNF474, ZNF479,ZNF48, ZNF480, ZNF483, ZNF484, ZNF485, ZNF486, ZNF487, ZNF488, ZNF490,ZNF491, ZNF492, ZNF493, ZNF496, ZNF497, ZNF500, ZNF501, ZNF502, ZNF503,ZNF506, ZNF507, ZNF510, ZNF511, ZNF512, ZNF512B, ZNF513, ZNF514, ZNF516,ZNF517, ZNF518A, ZNF518B, ZNF519, ZNF521, ZNF524, ZNF525, ZNF526,ZNF527, ZNF528, ZNF529, ZNF530, ZNF532, ZNF534, ZNF536, ZNF540, ZNF541,ZNF543, ZNF544, ZNF546, ZNF547, ZNF548, ZNF549, ZNF550, ZNF551, ZNF552,ZNF554, ZNF555, ZNF556, ZNF557, ZNF558, ZNF559, ZNF560, ZNF561, ZNF562,ZNF563, ZNF564, ZNF565, ZNF566, ZNF567, ZNF568, ZNF569, ZNF57, ZNF570,ZNF571, ZNF572, ZNF573, ZNF574, ZNF575, ZNF576, ZNF577, ZNF578, ZNF579,ZNF580, ZNF581, ZNF582, ZNF583, ZNF584, ZNF585A, ZNF585B, ZNF586,ZNF587, ZNF587B, ZNF589, ZNF592, ZNF594, ZNF595, ZNF596, ZNF597, ZNF598,ZNF599, ZNF600, ZNF605, ZNF606, ZNF607, ZNF608, ZNF609, ZNF610, ZNF611,ZNF613, ZNF614, ZNF615, ZNF616, ZNF618, ZNF619, ZNF620, ZNF621, ZNF623,ZNF624, ZNF625, ZNF626, ZNF627, ZNF628, ZNF629, ZNF630, ZNF639, ZNF641,ZNF644, ZNF645, ZNF646, ZNF648, ZNF649, ZNF652, ZNF653, ZNF654, ZNF655,ZNF658, ZNF66, ZNF660, ZNF662, ZNF664, ZNF665, ZNF667, ZNF668, ZNF669,ZNF670, ZNF671, ZNF672, ZNF674, ZNF675, ZNF676, ZNF677, ZNF678, ZNF679,ZNF680, ZNF681, ZNF682, ZNF683, ZNF684, ZNF687, ZNF688, ZNF689, ZNF69,ZNF691, ZNF692, ZNF695, ZNF696, ZNF697, ZNF699, ZNF7, ZNF70, ZNF700,ZNF701, ZNF703, ZNF704, ZNF705A, ZNF705B, ZNF705D, ZNF705E, ZNF705G,ZNF706, ZNF707, ZNF708, ZNF709, ZNF71, ZNF710, ZNF711, ZNF713, ZNF714,ZNF716, ZNF717, ZNF718, ZNF721, ZNF724, ZNF726, ZNF727, ZNF728, ZNF729,ZNF730, ZNF732, ZNF735, ZNF736, ZNF737, ZNF74, ZNF740, ZNF746, ZNF747,ZNF749, ZNF750, ZNF75A, ZNF75D, ZNF76, ZNF761, ZNF763, ZNF764, ZNF765,ZNF766, ZNF768, ZNF77, ZNF770, ZNF771, ZNF772, ZNF773, ZNF774, ZNF775,ZNF776, ZNF777, ZNF778, ZNF780A, ZNF780B, ZNF781, ZNF782, ZNF783,ZNF784, ZNF785, ZNF786, ZNF787, ZNF788, ZNF789, ZNF79, ZNF790, ZNF791,ZNF792, ZNF793, ZNF799, ZNF8, ZNF80, ZNF800, ZNF804A, ZNF804B, ZNF805,ZNF808, ZNF81, ZNF813, ZNF814, ZNF816, ZNF821, ZNF823, ZNF827, ZNF829,ZNF83, ZNF830, ZNF831, ZNF835, ZNF836, ZNF837, ZNF84, ZNF841, ZNF843,ZNF844, ZNF845, ZNF846, ZNF85, ZNF850, ZNF852, ZNF853, ZNF860, ZNF865,ZNF878, ZNF879, ZNF880, ZNF883, ZNF888, ZNF891, ZNF90, ZNF91, ZNF92,ZNF93, ZNF98, ZNF99, ZSCAN1, ZSCAN10, ZSCAN12, ZSCAN16, ZSCAN18, ZSCAN2,ZSCAN20, ZSCAN21, ZSCAN22, ZSCAN23, ZSCAN25, ZSCAN26, ZSCAN29, ZSCAN30,ZSCAN31, ZSCAN32, ZSCAN4, ZSCAN5A, ZSCAN5B, ZSCAN5C, ZSCAN9, ZUFSP,ZXDA, ZXDB, ZXDC, and ZZZ3.

In various aspects, the methods may be used to analyze the interactionof one or more transcription co-regulators with a region of chromatin.The transcription co-regulator may be a co-activator or a co-repressor.Non-limiting examples of transcription co-regulators that may beanalyzed using the methods described herein include: androgen receptorassociated proteins (e.g., ARA54, ARA55, and ARA70), AIRE, BCAS3,CREB-binding protein, CREB regulated transcription coactivators (e.g.,CRTC1, CRTC2, CRTC3), coactivator-associated arginine methyltransferase1 (CARM1), nuclear receptor coactivators (e.g., NCOA1, NCOA2, NCOA3,NCOA4, NCOA5, NCOA6, NCOA7), p300, PCAF, PGC1, PPARGC1A, PPARGC1B,PNRC1, PNRC2, CtBP, LCoR, nuclear receptor co-repressors (e.g., NCOR1,NCOR2), retinoblastoma protein (Rb), REST corepressors (e.g., RCOR1,RCOR2, RCOR3), SIN3A, SIN3B, TIF1, TRIM24, TRIM28, TRIM33, NSD1, PELP1,and RIP140.

In various aspects, the methods may be used to analyze the interactionof one or more histones with a region of chromatin. Non-limitingexamples of histones that may be analyzed using the methods describedherein include: members of the H1 family (e.g., H1F0, H1FNT, H1FOO,H1FX, HIST1H1A, HIST1H1B, HIST1H1C, HIST1H1D, HIST1H1E, HIST1H1T),members of the H2A family (e.g., H2AF, H2AFB1, H2AFB2, H2AFB3, H2AFJ,H2AFV, H2AFX, H2AFY, H2AFY2, H2AFZ, HIST1H2AA, HIST1H2AB, HIST1H2AC,HIST1H2AD, HIST1H2AE, HIST1H2AG, HIST1H2AI, HIST1H2AJ, HIST1H2AK,HIST1H2AL, HIST1H2AM, HIST2H2AA3, HIST2H2AC), members of the H2B family(e.g., H2BFM, H2BFS, H2BFWT, HIST1H2BA, HIST1H2BB, HIST1H2BC, HIST1H2BD,HIST1H2BE, HIST1H2BF, HIST1H2BG, HIST1H2BH, HIST1H2BI, HIST1H2BJ,HIST1H2BK, HIST1H2BL, HIST1H2BM, HIST1H2BN, HIST1H2B0, HIST2H2BE),members of the H3 family (e.g., HIST1H3A, HIST1H3B, HIST1H3C, HIST1H3D,HIST1H3E, HIST1H3F, HIST1H3G, HIST1H3H, HIST1H3I, HIST1H3J, HIST2H3C,HIST3H3), and members of the H4 family (e.g., HIST1H4A, HIST1H4B,HIST1H4C, HIST1H4D, HIST1H4E, HIST1H4F, HIST1H4G, HIST1H4H, HIST1H4I,HIST1H4J, HIST1H4K, HIST1H4L, HIST4H4).

In various aspects, the methods may be used to analyze one or morehistone modifications associated with a region of chromatin. Histonemodifications may include any type of modification to a histone protein,including, without limitation, lysine methylation (e.g.,monomethylation, dimethylation, trimethylation), arginine methylation(e.g., monomethylation, symmetrical dimethylation, asymmetricdimethylation), arginine citrullination, lysine acetylation, serinephosphorylation, threonine phosphorylation, tyrosine phosphorylation,modification of serine and/or threonine side chains with singleO—N-acetylglucosamine (O-GlcNAc) sugar residues, ADP ribosylation ofglutamate and/or arginine residues (e.g., mono-ADP ribosylation,poly-ADP ribosylation), ubiquitylation (e.g., mono-ubiquitylation,poly-ubiquitylation), and sumoylation. Non-limiting examples of histonemodifications that may be analyzed using the methods described hereininclude: H2AS1p, H2AK5ac, H2AK119ub, H2AT120p, H2AXS139p, H2AXY142p,H2BK5ac, H2BK12ac, H2BS14p, H2BK15ac, H2BK20ac, H2BK120ub, H3R2me,H3T3p, H3K4ac, H3K4me, H3T6p, H3R8me, H3K9ac, H3K9me, H3S10p, H3T11p,H3K14ac, H3R17me, H3K18ac, H3K23ac, H3R26me, H3K27me, H3S28p, H3K36ac,H3K36m, H3T45p, H3K56ac, H3K79me, H4S1p, H4R3me, H4K5ac, H4K8ac,H4K12ac, H4K16ac, H4K20me, and H4K91ac.

In various aspects, the methods may be used to analyze the interactionof one or more proteins involved in epigenetic regulation with a regionof chromatin. Non-limiting examples of proteins involves in epigeneticregulation that may be analyzed using the methods described hereininclude (listed by HGNC symbol): HDGFL2, A1CF, ACTB, ACTL6A, ACTL6B,ACTR3B, ACTR5, ACTR6, ACTR8, ADNP, AEBP2, AICDA, AIRE, ALKBH1, ANKRD32,ANP32A, ANP32B, ANP32E, APBB1, APEX1, APOBEC1, APOBEC2, APOBEC3A,APOBEC3B, APOBEC3C, APOBEC3D, APOBEC3F, APOBEC3G, APOBEC3H, ARID1A,ARID1B, ARID2, ARID4A, ARID4B, ARNTL, ARRB1, ASF1A, ASF1B, ASH1L, ASH2L,ASXL1, ASXL2, ASXL3, ATAD2, ATAD2B, ATF2, ATF7IP, ATM, ATN1, ATR, ATRX,ATXN7, ATXN7L3, AURKA, AURKB, AURKC, BABAM1, BAHD1, BANP, BAP1, BARD1,BAZ1A, BAZ1B, BAZ2A, BAZ2B, BCOR, BCORL1, BMI1, BPTF, BRCA1, BRCA2,BRCC3, BRD1, BRD2, BRD3, BRD4, BRD7, BRD8, BRD9, BRDT, BRE, BRMS1,BRMS1L, BRPF1, BRPF3, BRWD1, BRWD3, BUB1, C11orf30, C14orf169, C17orf49,CARM1, CBX1, CBX2, CBX3, CBX4, CBX5, CBX6, CBX7, CBX8, CCDC101, CDC6,CDC73, CDK1, CDK17, CDK2, CDK3, CDK5, CDK7, CDK9, CDY1, CDY1B, CDY2A,CDY2B, CDYL, CDYL2, CECR2, CENPC, CHAF1A, CHAF1B, CHD1, CHD1L, CHD2,CHD3, CHD4, CHD5, CHD6, CHD7, CHD8, CHD9, CHEK1, CHRAC1, CHTOP, CHUK,CIR1, CIT, CLNS1A, CLOCK, CRB2, CREBBP, CSNK2A1, CSRP2BP, CTBP1, CTBP2,CTCF, CTCFL, CTR9, CUL1, CUL2, CUL3, CUL4A, CUL4B, CUL5, CXXC1, DAPK3,DAXX, DDB1, DDB2, DDX21, DDX50, DEK, DMAP1, DNAJC1, DNAJC2, DND1, DNMT1,DNMT3A, DNMT3B, DNMT3L, DNTTIP2, DOT1L, DPF1, DPF2, DPF3, DPPA3, DPY30,DR1, DTX3L, DZIP3, E2F6, EED, EHMT1, EHMT2, EID1, EID2, EID2B, ELP2,ELP3, ELP4, ELP5, ELP6, ENY2, EP300, EP400, EPC1, EPC2, ERBB4, ERCC6,EXOSC1, EXOSC2, EXOSC3, EXOSC4, EXOSC5, EXOSC6, EXOSC7, EXOSC8, EXOSC9,EYA1, EYA2, EYA3, EYA4, EZH1, EZH2, FAM175A, FAM175B, FBL, FBRS, FBRSL1,FOXA1, FOXO1, FOXP1, FOXP2, FOXP3, FOXP4, GADD45A, GADD45B, GADD45G,GATAD1, GATAD2A, GATAD2B, GFI1, GFI1B, GLYR1, GSE1, GSG2, GTF2I, GTF3C4,HAT1, HCFC1, HCFC2, HDAC1, HDAC10, HDAC11, HDAC2, HDAC3, HDAC4, HDAC5,HDAC6, HDAC7, HDAC8, HDAC9, HDGF, HELLS, HIF1AN, HINFP, HIRA, HIRIP3,HJURP, HLCS, HLTF, HMG20A, HMG20B, HMGB1, HMGN1, HMGN2, HMGN3, HMGN4,HMGN5, HP1BP3, HR, HSPA1A, HSPA1B, HUWE1, IKBKAP, IKZF1, IKZF3, ING1,ING2, ING3, ING4, ING5, IN080, INO80B, INO80C, INO80D, INO80E, JADE1,JADE2, JADE3, JAK2, JARID2, JDP2, JMJD1C, JMJD6, KANSL1, KANSL2, KANSL3,KAT2A, KAT2B, KAT5, KAT6A, KAT6B, KAT7, KATE, KDM1A, KDM1B, KDM2A,KDM2B, KDM3A, KDM3B, KDM4A, KDM4B, KDM4C, KDM4D, KDM4E, KDM5A, KDM5B,KDM5C, KDM5D, KDM6A, KDM6B, KDM7A, KDM8, KEAP1, KMT2A, KMT2B, KMT2C,KMT2D, KMT2E, L3MBTL1, L3MBTL2, L3MBTL3, L3MBTL4, LAS1L, LBR, LEO1,LRWD1, MAP3K7, MAPKAPK3, MASTL, MAX, MAZ, MBD1, MBD2, MBD3, MBD4, MBD5,MBD6, MBIP, MBTD1, MCRS1, MDC1, MEAF6, MECP2, MEN1, MGA, MGEA5, MINA,MLLT1, MLLT10, MLLT6, MORF4L1, MORF4L2, MOV10, MPHOSPH8, MRGBP, MSH6,MSL1, MSL2, MSL3, MST1, MTA1, MTA2, MTA3, MTF2, MUM1, MYBBP1A, MYO1C,MYSM1, NAA60, NAP1L1, NAP1L2, NAP1L4, NASP, NAT10, NBN, NCL, NCOA1,NCOA2, NCOA3, NCOA6, NCOR1, NCOR2, NEK6, NEK9, NFRKB, NFYB, NFYC, NIPBL,NOC2L, NPAS2, NPM1, NPM2, NSD1, NSL1, OGT, PADI1, PADI2, PADI3, PADI4,PAF1, PAGR1, PAK2, PARG, PARP1, PARP2, PARP3, PAXIP1, PBK, PBRM1, PCGF1,PCGF2, PCGF3, PCGF5, PCGF6, PCNA, PDP1, PELP1, PHC1, PHC2, PHC3, PHF1,PHF10, PHF12, PHF13, PHF14, PHF19, PHF2, PHF20, PHF20L1, PHF21A, PHF8,PHIP, PIWIL4, PKM, PKN1, POGZ, POLE3, PPARGC1A, PPM1G, PPP2CA, PPP4C,PPP4R2, PRDM1, PRDM11, PRDM12, PRDM13, PRDM14, PRDM16, PRDM2, PRDM4,PRDM5, PRDM6, PRDM7, PRDM8, PRDM9, PRKAA1, PRKAA2, PRKAB1, PRKAB2,PRKAG1, PRKAG2, PRKAG3, PRKCA, PRKCB, PRKCD, PRKDC, PRMT1, PRMT2, PRMT5,PRMT6, PRMT7, PRMT8, PRMT9, PRPF31, PRR14, PSIP1, RAD51, RAD54B, RAD54L,RAD54L2, RAG1, RAG2, RAI1, RARA, RB1, RBBP4, RBBP5, RBBP7, RBX1, RCC1,RCOR1, RCOR3, REST, RING1, RLIM, RMI1, RNF168, RNF2, RNF20, RNF40, RNF8,RPS6KA3, RPS6KA4, RPS6KA5, RRP8, RSF1, RUVBL1, RUVBL2, RYBP, SAFB,SAP130, SAP18, SAP25, SAP30, SAP30L, SATB1, SATB2, SCMH1, SCML2, SCML4,SENP1, SENP3, SET, SETD1A, SETD1B, SETD2, SETD3, SETD5, SETD6, SETD7,SETD8, SETDB1, SETDB2, SETMAR, SF3B1, SF3B3, SFMBT1, SFMBT2, SFPQ,SHPRH, SIN3A, SIN3B, SIRT1, SIRT2, SIRT6, SIRT7, SKP1, SMARCA1, SMARCA2,SMARCA4, SMARCA5, SMARCAD1, SMARCAL1, SMARCB1, SMARCC1, SMARCC2,SMARCD1, SMARCD2, SMARCD3, SMARCE1, SMEK1, SMEK2, SMYD1, SMYD2, SMYD3,SMYD4, SNAI2, SP1, SP100, SP140, SPEN, SPOP, SRCAP, SRSF1, SRSF3,SS18L1, SS18L2, SSRP1, STK4, SUDS3, SUPT16H, SUPT3H, SUPT6H, SUPT7L,SUV39H1, SUV39H2, SUV420H1, SUV420H2, SUZ12, SYNCRIP, TADA1, TADA2A,TADA2B, TADA3, TAF1, TAF10, TAF12, TAF1L, TAF2, TAF3, TAF4, TAF5, TAF5L,TAF6, TAF6L, TAF7, TAF8, TAF9, TAF9B, TBL1XR1, TDG, TDRD3, TDRD7, TDRKH,TET1, TET2, TET3, TEX10, TFDP1, TFPT, TLE1, TLE2, TLE4, TLK1, TLK2,TNP1, TNP2, TONSL, TOP2A, TOP2B, TP53, TP53BP1, TRIM16, TRIM24, TRIM27,TRIM28, TRIM33, TRRAP, TSSK6, TTK, TYW5, UBE2A, UBE2B, UBE2D1, UBE2D3,UBE2E1, UBE2H, UBE2N, UBE2T, UBN1, UBR2, UBR5, UBR7, UCHL5, UHRF1,UHRF2, UIMC1, USP11, USP12, USP15, USP16, USP17L2, USP21, USP22, USP3,USP36, USP44, USP46, USP49, USP7, UTY, VDR, VPS72, VRK1, WAC, WDR5,WDR77, WDR82, WHSC1, WHSC1L1, WSB2, YAF2, YEATS2, YEATS4, YWHAB, YWHAE,YWHAZ, YY1, ZBTB16, ZBTB33, ZBTB7C, ZCWPW1, ZFP57, ZGPAT, ZHX1, ZMYM2,ZMYM3, ZMYND11, ZMYND8, ZNF217, ZNF516, ZNF532, ZNF541, ZNF592, ZNF687,ZNF711, ZNHIT1, ZRANB3, and ZZZ3.

In various aspects, the methods may be used to analyze the interactionof one or more protein complexes with a region of chromatin.Non-limiting examples of protein complexes that may be analyzed usingthe methods described herein include: ACF, B-WICH, RSF, CHRAC, NoRC,NuRF, CERF, BAF, nBAF, npBAF, PBAF, SWI/SNF_Brg1(I), SWI/SNF_Brg1(II),SWI/SNF_Brm, SWI/SNF-like_EPAFa, WINAC, CERF, SWI/SNF-like EPAFB, bBAF,SWI/SNF BRM-BRG1, Ino80, SWR, APOB_mRNA_editosome, PCAF, HBO1, TFTC-HAT,Pol2 elongator, NuA4, Piccolo_NuA4, MOZ/MORF, SAGA, ATAC, NSL,NuA4-related complex, STAGA, NuRD, BHC, MeCP1, mSin3A, core HDAC,mSin3A-like complex, PRC1, BCOR, RING2-L3MBTL2, RING2-FBRS, PRC2,COMPASS, Menin-associated_HMT, MLL-HCF, methylosome, eNoSc, CHD8,MLL2/3, COMPASS-like MLL1,2, MLL4/WBP7, COMPASS-like MLL3,4, FACT,SRCAP, BRISC, PR-DUB, BRCC, BRCA1-A, CAF-1, CREST-BRG1, RNA exosome,PPP4C-PPP4R2-PPP4R3A, L3MBTL1, SCL, and LSD-CoREST.

Systems and Methods for Sample Compartmentalization

In an aspect, the systems and methods described herein provide for thecompartmentalization, depositing, or partitioning of one or moreparticles (e.g., biological particles, macromolecular constituents ofbiological particles, beads, reagents, etc.) into discrete compartmentsor partitions (referred to interchangeably herein as partitions), whereeach partition maintains separation of its own contents from thecontents of other partitions. The partition can be a droplet in anemulsion. A partition may comprise one or more other partitions.

A partition may include one or more particles. A partition may includeone or more types of particles. For example, a partition of the presentdisclosure may comprise one or more biological particles and/ormacromolecular constituents thereof. A partition may comprise one ormore gel beads. A partition may comprise one or more cell beads. Apartition may include a single gel bead, a single cell bead, or both asingle cell bead and single gel bead. A partition may include one ormore reagents. Alternatively, a partition may be unoccupied. Forexample, a partition may not comprise a bead. A cell bead can be abiological particle and/or one or more of its macromolecularconstituents encased inside of a gel or polymer matrix, such as viapolymerization of a droplet containing the biological particle andprecursors capable of being polymerized or gelled. Unique identifiers,such as barcodes, may be injected into the droplets previous to,subsequent to, or concurrently with droplet generation, such as via amicrocapsule (e.g., bead), as described elsewhere herein. Microfluidicchannel networks (e.g., on a chip) can be utilized to generatepartitions as described herein. Alternative mechanisms may also beemployed in the partitioning of individual biological particles,including porous membranes through which aqueous mixtures of cells areextruded into non-aqueous fluids.

The partitions can be flowable within fluid streams. The partitions maycomprise, for example, micro-vesicles that have an outer barriersurrounding an inner fluid center or core. In some cases, the partitionsmay comprise a porous matrix that is capable of entraining and/orretaining materials within its matrix. The partitions can be droplets ofa first phase within a second phase, wherein the first and second phasesare immiscible. For example, the partitions can be droplets of aqueousfluid within a non-aqueous continuous phase (e.g., oil phase). Inanother example, the partitions can be droplets of a non-aqueous fluidwithin an aqueous phase. In some examples, the partitions may beprovided in a water-in-oil emulsion or oil-in-water emulsion. A varietyof different vessels are described in, for example, U.S. PatentApplication Publication No. 2014/0155295, which is entirely incorporatedherein by reference for all purposes. Emulsion systems for creatingstable droplets in non-aqueous or oil continuous phases are describedin, for example, U.S. Patent Application Publication No. 2010/0105112,which is entirely incorporated herein by reference for all purposes.

In the case of droplets in an emulsion, allocating individual particlesto discrete partitions may in one non-limiting example be accomplishedby introducing a flowing stream of particles in an aqueous fluid into aflowing stream of a non-aqueous fluid, such that droplets are generatedat the junction of the two streams. Fluid properties (e.g., fluid flowrates, fluid viscosities, etc.), particle properties (e.g., volumefraction, particle size, particle concentration, etc.), microfluidicarchitectures (e.g., channel geometry, etc.), and other parameters maybe adjusted to control the occupancy of the resulting partitions (e.g.,number of biological particles per partition, number of beads perpartition, etc.). For example, partition occupancy can be controlled byproviding the aqueous stream at a certain concentration and/or flow rateof particles. To generate single biological particle partitions, therelative flow rates of the immiscible fluids can be selected such that,on average, the partitions may contain less than one biological particleper partition in order to ensure that those partitions that are occupiedare primarily singly occupied. In some cases, partitions among aplurality of partitions may contain at most one biological particle(e.g., bead, DNA, cell or cellular material). In some embodiments, thevarious parameters (e.g., fluid properties, particle properties,microfluidic architectures, etc.) may be selected or adjusted such thata majority of partitions are occupied, for example, allowing for only asmall percentage of unoccupied partitions. The flows and channelarchitectures can be controlled as to ensure a given number of singlyoccupied partitions, less than a certain level of unoccupied partitionsand/or less than a certain level of multiply occupied partitions.

FIG. 1 shows an example of a microfluidic channel structure 100 forpartitioning individual biological particles. The channel structure 100can include channel segments 102, 104, 106 and 108 communicating at achannel junction 110. In operation, a first aqueous fluid 112 thatincludes suspended biological particles (or cells) 114 may betransported along channel segment 102 into junction 110, while a secondfluid 116 that is immiscible with the aqueous fluid 112 is delivered tothe junction 110 from each of channel segments 104 and 106 to creatediscrete droplets 118, 120 of the first aqueous fluid 112 flowing intochannel segment 108, and flowing away from junction 110. The channelsegment 108 may be fluidically coupled to an outlet reservoir where thediscrete droplets can be stored and/or harvested. A discrete dropletgenerated may include an individual biological particle 114 (such asdroplets 118). A discrete droplet generated may include more than oneindividual biological particle 114 (not shown in FIG. 1). A discretedroplet may contain no biological particle 114 (such as droplet 120).Each discrete partition may maintain separation of its own contents(e.g., individual biological particle 114) from the contents of otherpartitions.

The second fluid 116 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets118, 120. Examples of particularly useful partitioning fluids andfluorosurfactants are described, for example, in U.S. Patent ApplicationPublication No. 2010/0105112, which is entirely incorporated herein byreference for all purposes.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 100 may have other geometries. For example, amicrofluidic channel structure can have more than one channel junction.For example, a microfluidic channel structure can have 2, 3, 4, or 5channel segments each carrying particles (e.g., biological particles,cell beads, and/or gel beads) that meet at a channel junction. Fluid maybe directed to flow along one or more channels or reservoirs via one ormore fluid flow units. A fluid flow unit can comprise compressors (e.g.,providing positive pressure), pumps (e.g., providing negative pressure),actuators, and the like to control flow of the fluid. Fluid may also orotherwise be controlled via applied pressure differentials, centrifugalforce, electrokinetic pumping, vacuum, capillary or gravity flow, or thelike.

The generated droplets may comprise two subsets of droplets: (1)occupied droplets 118, containing one or more biological particles 114,and (2) unoccupied droplets 120, not containing any biological particles114. Occupied droplets 118 may comprise singly occupied droplets (havingone biological particle) and multiply occupied droplets (having morethan one biological particle). As described elsewhere herein, in somecases, the majority of occupied partitions can include no more than onebiological particle per occupied partition and some of the generatedpartitions can be unoccupied (of any biological particle). In somecases, though, some of the occupied partitions may include more than onebiological particle. In some cases, the partitioning process may becontrolled such that fewer than about 25% of the occupied partitionscontain more than one biological particle, and in many cases, fewer thanabout 20% of the occupied partitions have more than one biologicalparticle, while in some cases, fewer than about 10% or even fewer thanabout 5% of the occupied partitions include more than one biologicalparticle per partition.

In some cases, it may be desirable to minimize the creation of excessivenumbers of empty partitions, such as to reduce costs and/or increaseefficiency. While this minimization may be achieved by providing asufficient number of biological particles (e.g., biological particles114) at the partitioning junction 110, such as to ensure that at leastone biological particle is encapsulated in a partition, the Poissoniandistribution may expectedly increase the number of partitions thatinclude multiple biological particles. As such, where singly occupiedpartitions are to be obtained, at most about 95%, 90%, 85%, 80%, 75%,70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% orless of the generated partitions can be unoccupied.

In some cases, the flow of one or more of the biological particles(e.g., in channel segment 102), or other fluids directed into thepartitioning junction (e.g., in channel segments 104, 106) can becontrolled such that, in many cases, no more than about 50% of thegenerated partitions, no more than about 25% of the generatedpartitions, or no more than about 10% of the generated partitions areunoccupied. These flows can be controlled so as to present anon-Poissonian distribution of single-occupied partitions whileproviding lower levels of unoccupied partitions. The above noted rangesof unoccupied partitions can be achieved while still providing any ofthe single occupancy rates described above. For example, in many cases,the use of the systems and methods described herein can create resultingpartitions that have multiple occupancy rates of less than about 25%,less than about 20%, less than about 15%, less than about 10%, and inmany cases, less than about 5%, while having unoccupied partitions ofless than about 50%, less than about 40%, less than about 30%, less thanabout 20%, less than about 10%, less than about 5%, or less.

As will be appreciated, the above-described occupancy rates are alsoapplicable to partitions that include both biological particles andadditional reagents, including, but not limited to, microcapsules orbeads (e.g., gel beads) carrying barcoded nucleic acid molecules (e.g.,oligonucleotides) (described in relation to FIG. 2). The occupiedpartitions (e.g., at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,90%, 95%, or 99% of the occupied partitions) can include both amicrocapsule (e.g., bead) comprising barcoded nucleic acid molecules anda biological particle.

In another aspect, in addition to or as an alternative to droplet basedpartitioning, biological particles may be encapsulated within amicrocapsule that comprises an outer shell, layer or porous matrix inwhich is entrained one or more individual biological particles or smallgroups of biological particles. The microcapsule may include otherreagents. Encapsulation of biological particles may be performed by avariety of processes. Such processes may combine an aqueous fluidcontaining the biological particles with a polymeric precursor materialthat may be capable of being formed into a gel or other solid orsemi-solid matrix upon application of a particular stimulus to thepolymer precursor. Such stimuli can include, for example, thermalstimuli (e.g., either heating or cooling), photo-stimuli (e.g., throughphoto-curing), chemical stimuli (e.g., through crosslinking,polymerization initiation of the precursor (e.g., through addedinitiators)), mechanical stimuli, or a combination thereof

Preparation of microcapsules comprising biological particles may beperformed by a variety of methods. For example, air knife droplet oraerosol generators may be used to dispense droplets of precursor fluidsinto gelling solutions in order to form microcapsules that includeindividual biological particles or small groups of biological particles.Likewise, membrane based encapsulation systems may be used to generatemicrocapsules comprising encapsulated biological particles as describedherein. Microfluidic systems of the present disclosure, such as thatshown in FIG. 1, may be readily used in encapsulating cells as describedherein. In particular, and with reference to FIG. 1, the aqueous fluid112 comprising (i) the biological particles 114 and (ii) the polymerprecursor material (not shown) is flowed into channel junction 110,where it is partitioned into droplets 118, 120 through the flow ofnon-aqueous fluid 116. In the case of encapsulation methods, non-aqueousfluid 116 may also include an initiator (not shown) to causepolymerization and/or crosslinking of the polymer precursor to form themicrocapsule that includes the entrained biological particles. Examplesof polymer precursor/initiator pairs include those described in U.S.Patent Application Publication No. 2014/0378345, which is entirelyincorporated herein by reference for all purposes.

For example, in the case where the polymer precursor material comprisesa linear polymer material, such as a linear polyacrylamide, PEG, orother linear polymeric material, the activation agent may comprise across-linking agent, or a chemical that activates a cross-linking agentwithin the formed droplets. Likewise, for polymer precursors thatcomprise polymerizable monomers, the activation agent may comprise apolymerization initiator. For example, in certain cases, where thepolymer precursor comprises a mixture of acrylamide monomer with aN,N′-bis-(acryloyl)cystamine (BAC) comonomer, an agent such astetraethylmethylenediamine (TEMED) may be provided within the secondfluid streams 116 in channel segments 104 and 106, which can initiatethe copolymerization of the acrylamide and BAC into a cross-linkedpolymer network, or hydrogel.

Upon contact of the second fluid stream 116 with the first fluid stream112 at junction 110, during formation of droplets, the TEMED may diffusefrom the second fluid 116 into the aqueous fluid 112 comprising thelinear polyacrylamide, which will activate the crosslinking of thepolyacrylamide within the droplets 118, 120, resulting in the formationof gel (e.g., hydrogel) microcapsules, as solid or semi-solid beads orparticles entraining the cells 114. Although described in terms ofpolyacrylamide encapsulation, other ‘activatable’ encapsulationcompositions may also be employed in the context of the methods andcompositions described herein. For example, formation of alginatedroplets followed by exposure to divalent metal ions (e.g., Ca²⁺ ions),can be used as an encapsulation process using the described processes.Likewise, agarose droplets may also be transformed into capsules throughtemperature based gelling (e.g., upon cooling, etc.).

In some cases, encapsulated biological particles can be selectivelyreleasable from the microcapsule, such as through passage of time orupon application of a particular stimulus, that degrades themicrocapsule sufficiently to allow the biological particles (e.g.,cell), or its other contents to be released from the microcapsule, suchas into a partition (e.g., droplet). For example, in the case of thepolyacrylamide polymer described above, degradation of the microcapsulemay be accomplished through the introduction of an appropriate reducingagent, such as DTT or the like, to cleave disulfide bonds thatcross-link the polymer matrix. See, for example, U.S. Patent ApplicationPublication No. 2014/0378345, which is entirely incorporated herein byreference for all purposes.

The biological particle can be subjected to other conditions sufficientto polymerize or gel the precursors. The conditions sufficient topolymerize or gel the precursors may comprise exposure to heating,cooling, electromagnetic radiation, and/or light. The conditionssufficient to polymerize or gel the precursors may comprise anyconditions sufficient to polymerize or gel the precursors. Followingpolymerization or gelling, a polymer or gel may be formed around thebiological particle. The polymer or gel may be diffusively permeable tochemical or biochemical reagents. The polymer or gel may be diffusivelyimpermeable to macromolecular constituents of the biological particle.In this manner, the polymer or gel may act to allow the biologicalparticle to be subjected to chemical or biochemical operations whilespatially confining the macromolecular constituents to a region of thedroplet defined by the polymer or gel. The polymer or gel may includeone or more of disulfide cross-linked polyacrylamide, agarose, alginate,polyvinyl alcohol, polyethylene glycol (PEG)-diacrylate, PEG-acrylate,PEG-thiol, PEG-azide, PEG-alkyne, other acrylates, chitosan, hyaluronicacid, collagen, fibrin, gelatin, or elastin. The polymer or gel maycomprise any other polymer or gel.

The polymer or gel may be functionalized to bind to targeted analytes,such as nucleic acids, proteins, carbohydrates, lipids or otheranalytes. The polymer or gel may be polymerized or gelled via a passivemechanism. The polymer or gel may be stable in alkaline conditions or atelevated temperature. The polymer or gel may have mechanical propertiessimilar to the mechanical properties of the bead. For instance, thepolymer or gel may be of a similar size to the bead. The polymer or gelmay have a mechanical strength (e.g. tensile strength) similar to thatof the bead. The polymer or gel may be of a lower density than an oil.The polymer or gel may be of a density that is roughly similar to thatof a buffer. The polymer or gel may have a tunable pore size. The poresize may be chosen to, for instance, retain denatured nucleic acids. Thepore size may be chosen to maintain diffusive permeability to exogenouschemicals such as sodium hydroxide (NaOH) and/or endogenous chemicalssuch as inhibitors. The polymer or gel may be biocompatible. The polymeror gel may maintain or enhance cell viability. The polymer or gel may bebiochemically compatible. The polymer or gel may be polymerized and/ordepolymerized thermally, chemically, enzymatically, and/or optically.

The polymer may comprise poly(acrylamide-co-acrylic acid) crosslinkedwith disulfide linkages. The preparation of the polymer may comprise atwo-step reaction. In the first activation step,poly(acrylamide-co-acrylic acid) may be exposed to an acylating agent toconvert carboxylic acids to esters. For instance, thepoly(acrylamide-co-acrylic acid) may be exposed to4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride(DMTMM). The polyacrylamide-co-acrylic acid may be exposed to othersalts of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium. Inthe second cross-linking step, the ester formed in the first step may beexposed to a disulfide crosslinking agent. For instance, the ester maybe exposed to cystamine (2,2′-dithiobis(ethylamine)). Following the twosteps, the biological particle may be surrounded by polyacrylamidestrands linked together by disulfide bridges. In this manner, thebiological particle may be encased inside of or comprise a gel or matrix(e.g., polymer matrix) to form a “cell bead.” A cell bead can containbiological particles (e.g., a cell) or macromolecular constituents(e.g., RNA, DNA, proteins, etc.) of biological particles. A cell beadmay include a single cell or multiple cells, or a derivative of thesingle cell or multiple cells. For example after lysing and washing thecells, inhibitory components from cell lysates can be washed away andthe macromolecular constituents can be bound as cell beads. Systems andmethods disclosed herein can be applicable to both cell beads (and/ordroplets or other partitions) containing biological particles and cellbeads (and/or droplets or other partitions) containing macromolecularconstituents of biological particles.

Encapsulated biological particles can provide certain potentialadvantages of being more storable and more portable than droplet-basedpartitioned biological particles. Furthermore, in some cases, it may bedesirable to allow biological particles to incubate for a select periodof time before analysis, such as in order to characterize changes insuch biological particles over time, either in the presence or absenceof different stimuli. In such cases, encapsulation may allow for longerincubation than partitioning in emulsion droplets, although in somecases, droplet partitioned biological particles may also be incubatedfor different periods of time, e.g., at least 10 seconds, at least 30seconds, at least 1 minute, at least 5 minutes, at least 10 minutes, atleast 30 minutes, at least 1 hour, at least 2 hours, at least 5 hours,or at least 10 hours or more. The encapsulation of biological particlesmay constitute the partitioning of the biological particles into whichother reagents are co-partitioned. Alternatively or in addition,encapsulated biological particles may be readily deposited into otherpartitions (e.g., droplets) as described above.

Beads

A partition may comprise one or more unique identifiers, such asbarcodes. Barcodes may be previously, subsequently or concurrentlydelivered to the partitions that hold the compartmentalized orpartitioned biological particle. For example, barcodes may be injectedinto droplets previous to, subsequent to, or concurrently with dropletgeneration. The delivery of the barcodes to a particular partitionallows for the later attribution of the characteristics of theindividual biological particle to the particular partition. Barcodes maybe delivered, for example on a nucleic acid molecule (e.g., anoligonucleotide), to a partition via any suitable mechanism. Barcodednucleic acid molecules can be delivered to a partition via amicrocapsule. A microcapsule, in some instances, can comprise a bead.Beads are described in further detail below.

In some cases, barcoded nucleic acid molecules can be initiallyassociated with the microcapsule and then released from themicrocapsule. Release of the barcoded nucleic acid molecules can bepassive (e.g., by diffusion out of the microcapsule). In addition oralternatively, release from the microcapsule can be upon application ofa stimulus which allows the barcoded nucleic acid nucleic acid moleculesto dissociate or to be released from the microcapsule. Such stimulus maydisrupt the microcapsule, an interaction that couples the barcodednucleic acid molecules to or within the microcapsule, or both. Suchstimulus can include, for example, a thermal stimulus, photo-stimulus,chemical stimulus (e.g., change in pH or use of a reducing agent(s)), amechanical stimulus, a radiation stimulus; a biological stimulus (e.g.,enzyme), or any combination thereof.

FIG. 2 shows an example of a microfluidic channel structure 200 fordelivering barcode carrying beads to droplets. The channel structure 200can include channel segments 201, 202, 204, 206 and 208 communicating ata channel junction 210. In operation, the channel segment 201 maytransport an aqueous fluid 212 that includes a plurality of beads 214(e.g., with nucleic acid molecules, oligonucleotides, molecular tags)along the channel segment 201 into junction 210. The plurality of beads214 may be sourced from a suspension of beads. For example, the channelsegment 201 may be connected to a reservoir comprising an aqueoussuspension of beads 214. The channel segment 202 may transport theaqueous fluid 212 that includes a plurality of biological particles 216along the channel segment 202 into junction 210. The plurality ofbiological particles 216 may be sourced from a suspension of biologicalparticles. For example, the channel segment 202 may be connected to areservoir comprising an aqueous suspension of biological particles 216.In some instances, the aqueous fluid 212 in either the first channelsegment 201 or the second channel segment 202, or in both segments, caninclude one or more reagents, as further described below. A second fluid218 that is immiscible with the aqueous fluid 212 (e.g., oil) can bedelivered to the junction 210 from each of channel segments 204 and 206.Upon meeting of the aqueous fluid 212 from each of channel segments 201and 202 and the second fluid 218 from each of channel segments 204 and206 at the channel junction 210, the aqueous fluid 212 can bepartitioned as discrete droplets 220 in the second fluid 218 and flowaway from the junction 210 along channel segment 208. The channelsegment 208 may deliver the discrete droplets to an outlet reservoirfluidly coupled to the channel segment 208, where they may be harvested.

As an alternative, the channel segments 201 and 202 may meet at anotherjunction upstream of the junction 210. At such junction, beads andbiological particles may form a mixture that is directed along anotherchannel to the junction 210 to yield droplets 220. The mixture mayprovide the beads and biological particles in an alternating fashion,such that, for example, a droplet comprises a single bead and a singlebiological particle.

Beads, biological particles and droplets may flow along channels atsubstantially regular flow profiles (e.g., at regular flow rates). Suchregular flow profiles may permit a droplet to include a single bead anda single biological particle. Such regular flow profiles may permit thedroplets to have an occupancy (e.g., droplets having beads andbiological particles) greater than 5%, 10%, 20%, 30%, 40%, 50%, 60%,70%, 80%, 90%, or 95%. Such regular flow profiles and devices that maybe used to provide such regular flow profiles are provided in, forexample, U.S. Patent Publication No. 2015/0292988, which is entirelyincorporated herein by reference.

The second fluid 218 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets220.

A discrete droplet that is generated may include an individualbiological particle 216. A discrete droplet that is generated mayinclude a barcode or other reagent carrying bead 214. A discrete dropletgenerated may include both an individual biological particle and abarcode carrying bead, such as droplets 220. In some instances, adiscrete droplet may include more than one individual biologicalparticle or no biological particle. In some instances, a discretedroplet may include more than one bead or no bead. A discrete dropletmay be unoccupied (e.g., no beads, no biological particles).

Beneficially, a discrete droplet partitioning a biological particle anda barcode carrying bead may effectively allow the attribution of thebarcode to macromolecular constituents of the biological particle withinthe partition. The contents of a partition may remain discrete from thecontents of other partitions.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 200 may have other geometries. For example, amicrofluidic channel structure can have more than one channel junctions.For example, a microfluidic channel structure can have 2, 3, 4, or 5channel segments each carrying beads that meet at a channel junction.Fluid may be directed flow along one or more channels or reservoirs viaone or more fluid flow units. A fluid flow unit can comprise compressors(e.g., providing positive pressure), pumps (e.g., providing negativepressure), actuators, and the like to control flow of the fluid. Fluidmay also or otherwise be controlled via applied pressure differentials,centrifugal force, electrokinetic pumping, vacuum, capillary or gravityflow, or the like.

A bead may be porous, non-porous, solid, semi-solid, semi-fluidic,fluidic, and/or a combination thereof. In some instances, a bead may bedissolvable, disruptable, and/or degradable. In some cases, a bead maynot be degradable. In some cases, the bead may be a gel bead. A gel beadmay be a hydrogel bead. A gel bead may be formed from molecularprecursors, such as a polymeric or monomeric species. A semi-solid beadmay be a liposomal bead. Solid beads may comprise metals including ironoxide, gold, and silver. In some cases, the bead may be a silica bead.In some cases, the bead can be rigid. In other cases, the bead may beflexible and/or compressible.

A bead may be of any suitable shape. Examples of bead shapes include,but are not limited to, spherical, non-spherical, oval, oblong,amorphous, circular, cylindrical, and variations thereof

Beads may be of uniform size or heterogeneous size. In some cases, thediameter of a bead may be at least about 10 nanometers (nm), 100 nm, 500nm, 1 micrometer (μm), 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm,70 μm, 80 μm, 90 μm, 100 μm, 250 μm, 500 μm, 1 mm, or greater. In somecases, a bead may have a diameter of less than about 10 nm, 100 nm, 500nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm,90 μm, 100 μm, 250 μm, 500 μm, 1mm, or less. In some cases, a bead mayhave a diameter in the range of about 40-75 μm, 30-75 μm, 20-75 μm,40-85 μm, 40-95 μm, 20-100 μm, 10-100 μm, 1-100 μm, 20-250 μm, or 20-500μm.

In certain aspects, beads can be provided as a population or pluralityof beads having a relatively monodisperse size distribution. Where itmay be desirable to provide relatively consistent amounts of reagentswithin partitions, maintaining relatively consistent beadcharacteristics, such as size, can contribute to the overallconsistency. In particular, the beads described herein may have sizedistributions that have a coefficient of variation in theircross-sectional dimensions of less than 50%, less than 40%, less than30%, less than 20%, and in some cases less than 15%, less than 10%, lessthan 5%, or less.

A bead may comprise natural and/or synthetic materials. For example, abead can comprise a natural polymer, a synthetic polymer or both naturaland synthetic polymers. Examples of natural polymers include proteinsand sugars such as deoxyribonucleic acid, rubber, cellulose, starch(e.g., amylose, amylopectin), proteins, enzymes, polysaccharides, silks,polyhydroxyalkanoates, chitosan, dextran, collagen, carrageenan,ispaghula, acacia, agar, gelatin, shellac, sterculia gum, xanthan gum,Corn sugar gum, guar gum, gum karaya, agarose, alginic acid, alginate,or natural polymers thereof. Examples of synthetic polymers includeacrylics, nylons, silicones, spandex, viscose rayon, polycarboxylicacids, polyvinyl acetate, polyacrylamide, polyacrylate, polyethyleneglycol, polyurethanes, polylactic acid, silica, polystyrene,polyacrylonitrile, polybutadiene, polycarbonate, polyethylene,polyethylene terephthalate, poly(chlorotrifluoroethylene), poly(ethyleneoxide), poly(ethylene terephthalate), polyethylene, polyisobutylene,poly(methyl methacrylate), poly(oxymethylene), polyformaldehyde,polypropylene, polystyrene, poly(tetrafluoroethylene), poly(vinylacetate), poly(vinyl alcohol), poly(vinyl chloride), poly(vinylidenedichloride), poly(vinylidene difluoride), poly(vinyl fluoride) and/orcombinations (e.g., co-polymers) thereof. Beads may also be formed frommaterials other than polymers, including lipids, micelles, ceramics,glass-ceramics, material composites, metals, other inorganic materials,and others.

In some instances, the bead may contain molecular precursors (e.g.,monomers or polymers), which may form a polymer network viapolymerization of the molecular precursors. In some cases, a precursormay be an already polymerized species capable of undergoing furtherpolymerization via, for example, a chemical cross-linkage. In somecases, a precursor can comprise one or more of an acrylamide or amethacrylamide monomer, oligomer, or polymer. In some cases, the beadmay comprise prepolymers, which are oligomers capable of furtherpolymerization. For example, polyurethane beads may be prepared usingprepolymers. In some cases, the bead may contain individual polymersthat may be further polymerized together. In some cases, beads may begenerated via polymerization of different precursors, such that theycomprise mixed polymers, co-polymers, and/or block co-polymers. In somecases, the bead may comprise covalent or ionic bonds between polymericprecursors (e.g., monomers, oligomers, linear polymers), nucleic acidmolecules (e.g., oligonucleotides), primers, and other entities. In somecases, the covalent bonds can be carbon-carbon bonds, thioether bonds,or carbon-heteroatom bonds.

Cross-linking may be permanent or reversible, depending upon theparticular cross-linker used. Reversible cross-linking may allow for thepolymer to linearize or dissociate under appropriate conditions. In somecases, reversible cross-linking may also allow for reversible attachmentof a material bound to the surface of a bead. In some cases, across-linker may form disulfide linkages. In some cases, the chemicalcross-linker forming disulfide linkages may be cystamine or a modifiedcystamine.

In some cases, disulfide linkages can be formed between molecularprecursor units (e.g., monomers, oligomers, or linear polymers) orprecursors incorporated into a bead and nucleic acid molecules (e.g.,oligonucleotides). Cystamine (including modified cystamines), forexample, is an organic agent comprising a disulfide bond that may beused as a crosslinker agent between individual monomeric or polymericprecursors of a bead. Polyacrylamide may be polymerized in the presenceof cystamine or a species comprising cystamine (e.g., a modifiedcystamine) to generate polyacrylamide gel beads comprising disulfidelinkages (e.g., chemically degradable beads comprisingchemically-reducible cross-linkers). The disulfide linkages may permitthe bead to be degraded (or dissolved) upon exposure of the bead to areducing agent.

In some cases, chitosan, a linear polysaccharide polymer, may becrosslinked with glutaraldehyde via hydrophilic chains to form a bead.Crosslinking of chitosan polymers may be achieved by chemical reactionsthat are initiated by heat, pressure, change in pH, and/or radiation.

In some cases, a bead may comprise an acrydite moiety, which in certainaspects may be used to attach one or more nucleic acid molecules (e.g.,barcode sequence, barcoded nucleic acid molecule, barcodedoligonucleotide, primer, or other oligonucleotide) to the bead. In somecases, an acrydite moiety can refer to an acrydite analogue generatedfrom the reaction of acrydite with one or more species, such as, thereaction of acrydite with other monomers and cross-linkers during apolymerization reaction. Acrydite moieties may be modified to formchemical bonds with a species to be attached, such as a nucleic acidmolecule (e.g., barcode sequence, barcoded nucleic acid molecule,barcoded oligonucleotide, primer, or other oligonucleotide). Acryditemoieties may be modified with thiol groups capable of forming adisulfide bond or may be modified with groups already comprising adisulfide bond. The thiol or disulfide (via disulfide exchange) may beused as an anchor point for a species to be attached or another part ofthe acrydite moiety may be used for attachment. In some cases,attachment can be reversible, such that when the disulfide bond isbroken (e.g., in the presence of a reducing agent), the attached speciesis released from the bead. In other cases, an acrydite moiety cancomprise a reactive hydroxyl group that may be used for attachment.

Functionalization of beads for attachment of nucleic acid molecules(e.g., oligonucleotides) may be achieved through a wide range ofdifferent approaches, including activation of chemical groups within apolymer, incorporation of active or activatable functional groups in thepolymer structure, or attachment at the pre-polymer or monomer stage inbead production.

For example, precursors (e.g., monomers, cross-linkers) that arepolymerized to form a bead may comprise acrydite moieties, such thatwhen a bead is generated, the bead also comprises acrydite moieties. Theacrydite moieties can be attached to a nucleic acid molecule (e.g.,oligonucleotide), which may include a priming sequence (e.g., a primerfor amplifying target nucleic acids, random primer, primer sequence formessenger RNA) and/or one or more barcode sequences. The one morebarcode sequences may include sequences that are the same for allnucleic acid molecules coupled to a given bead and/or sequences that aredifferent across all nucleic acid molecules coupled to the given bead.The nucleic acid molecule may be incorporated into the bead.

In some cases, the nucleic acid molecule can comprise a functionalsequence, for example, for attachment to a sequencing flow cell, suchas, for example, a P5 sequence for Illumina® sequencing. In some cases,the nucleic acid molecule or derivative thereof (e.g., oligonucleotideor polynucleotide generated from the nucleic acid molecule) can compriseanother functional sequence, such as, for example, a P7 sequence forattachment to a sequencing flow cell for Illumina sequencing. In somecases, the nucleic acid molecule can comprise a barcode sequence. Insome cases, the primer can further comprise a unique molecularidentifier (UMI). In some cases, the primer can comprise an R1 primersequence for Illumina sequencing. In some cases, the primer can comprisean R2 primer sequence for Illumina sequencing. Examples of such nucleicacid molecules (e.g., oligonucleotides, polynucleotides, etc.) and usesthereof, as may be used with compositions, devices, methods and systemsof the present disclosure, are provided in U.S. Patent Pub. Nos.2014/0378345 and 2015/0376609, each of which is entirely incorporatedherein by reference.

FIG. 8 illustrates an example of a barcode carrying bead. A nucleic acidmolecule 802, such as an oligonucleotide, can be coupled to a bead 804by a releasable linkage 806, such as, for example, a disulfide linker.The same bead 804 may be coupled (e.g., via releasable linkage) to oneor more other nucleic acid molecules 818, 820. The nucleic acid molecule802 may be or comprise a barcode. As noted elsewhere herein, thestructure of the barcode may comprise a number of sequence elements. Thenucleic acid molecule 802 may comprise a functional sequence 808 thatmay be used in subsequent processing. For example, the functionalsequence 808 may include one or more of a sequencer specific flow cellattachment sequence (e.g., a P5 sequence for Illumina® sequencingsystems) and a sequencing primer sequence (e.g., a R1 primer forIllumina® sequencing systems). The nucleic acid molecule 802 maycomprise a barcode sequence 810 for use in barcoding the sample (e.g.,DNA, RNA, protein, etc.). In some cases, the barcode sequence 810 can bebead-specific such that the barcode sequence 810 is common to allnucleic acid molecules (e.g., including nucleic acid molecule 802)coupled to the same bead 804. Alternatively or in addition, the barcodesequence 810 can be partition-specific such that the barcode sequence810 is common to all nucleic acid molecules coupled to one or more beadsthat are partitioned into the same partition. The nucleic acid molecule802 may comprise a specific priming sequence 812, such as an mRNAspecific priming sequence (e.g., poly-T sequence), a targeted primingsequence, and/or a random priming sequence. The nucleic acid molecule802 may comprise an anchoring sequence 814 to ensure that the specificpriming sequence 812 hybridizes at the sequence end (e.g., of the mRNA).For example, the anchoring sequence 814 can include a random shortsequence of nucleotides, such as a 1-mer, 2-mer, 3-mer or longersequence, which can ensure that a poly-T segment is more likely tohybridize at the sequence end of the poly-A tail of the mRNA.

The nucleic acid molecule 802 may comprise a unique molecularidentifying sequence 816 (e.g., unique molecular identifier (UMI)). Insome cases, the unique molecular identifying sequence 816 may comprisefrom about 5 to about 8 nucleotides. Alternatively, the unique molecularidentifying sequence 816 may compress less than about 5 or more thanabout 8 nucleotides. The unique molecular identifying sequence 816 maybe a unique sequence that varies across individual nucleic acidmolecules (e.g., 802, 818, 820, etc.) coupled to a single bead (e.g.,bead 804). In some cases, the unique molecular identifying sequence 816may be a random sequence (e.g., such as a random N-mer sequence). Forexample, the UMI may provide a unique identifier of the starting mRNAmolecule that was captured, in order to allow quantitation of the numberof original expressed RNA. As will be appreciated, although FIG. 8 showsthree nucleic acid molecules 802, 818, 820 coupled to the surface of thebead 804, an individual bead may be coupled to any number of individualnucleic acid molecules, for example, from one to tens to hundreds ofthousands or even millions of individual nucleic acid molecules. Therespective barcodes for the individual nucleic acid molecules cancomprise both common sequence segments or relatively common sequencesegments (e.g., 808, 810, 812, etc.) and variable or unique sequencesegments (e.g., 816) between different individual nucleic acid moleculescoupled to the same bead.

In operation, a biological particle (e.g., cell, DNA, RNA, etc.) can beco-partitioned along with a barcode bearing bead 804. The barcodednucleic acid molecules 802, 818, 820 can be released from the bead 804in the partition. By way of example, in the context of analyzing sampleRNA, the poly-T segment (e.g., 812) of one of the released nucleic acidmolecules (e.g., 802) can hybridize to the poly-A tail of a mRNAmolecule. Reverse transcription may result in a cDNA transcript of themRNA, but which transcript includes each of the sequence segments 808,810, 816 of the nucleic acid molecule 802. Because the nucleic acidmolecule 802 comprises an anchoring sequence 814, it will more likelyhybridize to and prime reverse transcription at the sequence end of thepoly-A tail of the mRNA. Within any given partition, all of the cDNAtranscripts of the individual mRNA molecules may include a commonbarcode sequence segment 810. However, the transcripts made from thedifferent mRNA molecules within a given partition may vary at the uniquemolecular identifying sequence 812 segment (e.g., UMI segment).Beneficially, even following any subsequent amplification of thecontents of a given partition, the number of different UMIs can beindicative of the quantity of mRNA originating from a given partition,and thus from the biological particle (e.g., cell). As noted above, thetranscripts can be amplified, cleaned up and sequenced to identify thesequence of the cDNA transcript of the mRNA, as well as to sequence thebarcode segment and the UMI segment. While a poly-T primer sequence isdescribed, other targeted or random priming sequences may also be usedin priming the reverse transcription reaction. Likewise, althoughdescribed as releasing the barcoded oligonucleotides into the partition,in some cases, the nucleic acid molecules bound to the bead (e.g., gelbead) may be used to hybridize and capture the mRNA on the solid phaseof the bead, for example, in order to facilitate the separation of theRNA from other cell contents.

In some cases, precursors comprising a functional group that is reactiveor capable of being activated such that it becomes reactive can bepolymerized with other precursors to generate gel beads comprising theactivated or activatable functional group. The functional group may thenbe used to attach additional species (e.g., disulfide linkers, primers,other oligonucleotides, etc.) to the gel beads. For example, someprecursors comprising a carboxylic acid (COOH) group can co-polymerizewith other precursors to form a gel bead that also comprises a COOHfunctional group. In some cases, acrylic acid (a species comprising freeCOOH groups), acrylamide, and bis(acryloyl)cystamine can beco-polymerized together to generate a gel bead comprising free COOHgroups. The COOH groups of the gel bead can be activated (e.g., via1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) andN-Hydroxysuccinimide (NHS) or4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride(DMTMM)) such that they are reactive (e.g., reactive to amine functionalgroups where EDC/NHS or DMTMM are used for activation). The activatedCOOH groups can then react with an appropriate species (e.g., a speciescomprising an amine functional group where the carboxylic acid groupsare activated to be reactive with an amine functional group) comprisinga moiety to be linked to the bead.

Beads comprising disulfide linkages in their polymeric network may befunctionalized with additional species via reduction of some of thedisulfide linkages to free thiols. The disulfide linkages may be reducedvia, for example, the action of a reducing agent (e.g., DTT, TCEP, etc.)to generate free thiol groups, without dissolution of the bead. Freethiols of the beads can then react with free thiols of a species or aspecies comprising another disulfide bond (e.g., via thiol-disulfideexchange) such that the species can be linked to the beads (e.g., via agenerated disulfide bond). In some cases, free thiols of the beads mayreact with any other suitable group. For example, free thiols of thebeads may react with species comprising an acrydite moiety. The freethiol groups of the beads can react with the acrydite via Michaeladdition chemistry, such that the species comprising the acrydite islinked to the bead. In some cases, uncontrolled reactions can beprevented by inclusion of a thiol capping agent such asN-ethylmalieamide or iodoacetate.

Activation of disulfide linkages within a bead can be controlled suchthat only a small number of disulfide linkages are activated. Controlmay be exerted, for example, by controlling the concentration of areducing agent used to generate free thiol groups and/or concentrationof reagents used to form disulfide bonds in bead polymerization. In somecases, a low concentration (e.g., molecules of reducing agent:gel beadratios of less than or equal to about 1:100,000,000,000, less than orequal to about 1:10,000,000,000, less than or equal to about1:1,000,000,000, less than or equal to about 1:100,000,000, less than orequal to about 1:10,000,000, less than or equal to about 1:1,000,000,less than or equal to about 1:100,000, less than or equal to about1:10,000) of reducing agent may be used for reduction. Controlling thenumber of disulfide linkages that are reduced to free thiols may beuseful in ensuring bead structural integrity during functionalization.In some cases, optically-active agents, such as fluorescent dyes may becoupled to beads via free thiol groups of the beads and used to quantifythe number of free thiols present in a bead and/or track a bead.

In some cases, addition of moieties to a gel bead after gel beadformation may be advantageous. For example, addition of anoligonucleotide (e.g., barcoded oligonucleotide) after gel beadformation may avoid loss of the species during chain transfertermination that can occur during polymerization. Moreover, smallerprecursors (e.g., monomers or cross linkers that do not comprise sidechain groups and linked moieties) may be used for polymerization and canbe minimally hindered from growing chain ends due to viscous effects. Insome cases, functionalization after gel bead synthesis can minimizeexposure of species (e.g., oligonucleotides) to be loaded withpotentially damaging agents (e.g., free radicals) and/or chemicalenvironments. In some cases, the generated gel may possess an uppercritical solution temperature (UCST) that can permit temperature drivenswelling and collapse of a bead. Such functionality may aid inoligonucleotide (e.g., a primer) infiltration into the bead duringsubsequent functionalization of the bead with the oligonucleotide.Post-production functionalization may also be useful in controllingloading ratios of species in beads, such that, for example, thevariability in loading ratio is minimized. Species loading may also beperformed in a batch process such that a plurality of beads can befunctionalized with the species in a single batch.

A bead injected or otherwise introduced into a partition may comprisereleasably, cleavably, or reversibly attached barcodes. A bead injectedor otherwise introduced into a partition may comprise activatablebarcodes. A bead injected or otherwise introduced into a partition maybe degradable, disruptable, or dissolvable beads.

Barcodes can be releasably, cleavably or reversibly attached to thebeads such that barcodes can be released or be releasable throughcleavage of a linkage between the barcode molecule and the bead, orreleased through degradation of the underlying bead itself, allowing thebarcodes to be accessed or be accessible by other reagents, or both. Innon-limiting examples, cleavage may be achieved through reduction ofdi-sulfide bonds, use of restriction enzymes, photo-activated cleavage,or cleavage via other types of stimuli (e.g., chemical, thermal, pH,enzymatic, etc.) and/or reactions, such as described elsewhere herein.Releasable barcodes may sometimes be referred to as being activatable,in that they are available for reaction once released. Thus, forexample, an activatable barcode may be activated by releasing thebarcode from a bead (or other suitable type of partition describedherein). Other activatable configurations are also envisioned in thecontext of the described methods and systems.

In addition to, or as an alternative to the cleavable linkages betweenthe beads and the associated molecules, such as barcode containingnucleic acid molecules (e.g., barcoded oligonucleotides), the beads maybe degradable, disruptable, or dissolvable spontaneously or uponexposure to one or more stimuli (e.g., temperature changes, pH changes,exposure to particular chemical species or phase, exposure to light,reducing agent, etc.). In some cases, a bead may be dissolvable, suchthat material components of the beads are solubilized when exposed to aparticular chemical species or an environmental change, such as a changetemperature or a change in pH. In some cases, a gel bead can be degradedor dissolved at elevated temperature and/or in basic conditions. In somecases, a bead may be thermally degradable such that when the bead isexposed to an appropriate change in temperature (e.g., heat), the beaddegrades. Degradation or dissolution of a bead bound to a species (e.g.,a nucleic acid molecule, e.g., barcoded oligonucleotide) may result inrelease of the species from the bead.

As will be appreciated from the above disclosure, the degradation of abead may refer to the disassociation of a bound or entrained speciesfrom a bead, both with and without structurally degrading the physicalbead itself. For example, the degradation of the bead may involvecleavage of a cleavable linkage via one or more species and/or methodsdescribed elsewhere herein. In another example, entrained species may bereleased from beads through osmotic pressure differences due to, forexample, changing chemical environments. By way of example, alterationof bead pore sizes due to osmotic pressure differences can generallyoccur without structural degradation of the bead itself. In some cases,an increase in pore size due to osmotic swelling of a bead can permitthe release of entrained species within the bead. In other cases,osmotic shrinking of a bead may cause a bead to better retain anentrained species due to pore size contraction.

A degradable bead may be introduced into a partition, such as a dropletof an emulsion or a well, such that the bead degrades within thepartition and any associated species (e.g., oligonucleotides) arereleased within the droplet when the appropriate stimulus is applied.The free species (e.g., oligonucleotides, nucleic acid molecules) mayinteract with other reagents contained in the partition. For example, apolyacrylamide bead comprising cystamine and linked, via a disulfidebond, to a barcode sequence, may be combined with a reducing agentwithin a droplet of a water-in-oil emulsion. Within the droplet, thereducing agent can break the various disulfide bonds, resulting in beaddegradation and release of the barcode sequence into the aqueous, innerenvironment of the droplet. In another example, heating of a dropletcomprising a bead-bound barcode sequence in basic solution may alsoresult in bead degradation and release of the attached barcode sequenceinto the aqueous, inner environment of the droplet.

Any suitable number of molecular tag molecules (e.g., primer, barcodedoligonucleotide) can be associated with a bead such that, upon releasefrom the bead, the molecular tag molecules (e.g., primer, e.g., barcodedoligonucleotide) are present in the partition at a pre-definedconcentration. Such pre-defined concentration may be selected tofacilitate certain reactions for generating a sequencing library, e.g.,amplification, within the partition. In some cases, the pre-definedconcentration of the primer can be limited by the process of producingnucleic acid molecule (e.g., oligonucleotide) bearing beads.

In some cases, beads can be non-covalently loaded with one or morereagents. The beads can be non-covalently loaded by, for instance,subjecting the beads to conditions sufficient to swell the beads,allowing sufficient time for the reagents to diffuse into the interiorsof the beads, and subjecting the beads to conditions sufficient tode-swell the beads. The swelling of the beads may be accomplished, forinstance, by placing the beads in a thermodynamically favorable solvent,subjecting the beads to a higher or lower temperature, subjecting thebeads to a higher or lower ion concentration, and/or subjecting thebeads to an electric field. The swelling of the beads may beaccomplished by various swelling methods. The de-swelling of the beadsmay be accomplished, for instance, by transferring the beads in athermodynamically unfavorable solvent, subjecting the beads to lower orhigh temperatures, subjecting the beads to a lower or higher ionconcentration, and/or removing an electric field. The de-swelling of thebeads may be accomplished by various de-swelling methods. Transferringthe beads may cause pores in the bead to shrink. The shrinking may thenhinder reagents within the beads from diffusing out of the interiors ofthe beads. The hindrance may be due to steric interactions between thereagents and the interiors of the beads. The transfer may beaccomplished microfluidically. For instance, the transfer may beachieved by moving the beads from one co-flowing solvent stream to adifferent co-flowing solvent stream. The swellability and/or pore sizeof the beads may be adjusted by changing the polymer composition of thebead.

In some cases, an acrydite moiety linked to a precursor, another specieslinked to a precursor, or a precursor itself can comprise a labile bond,such as chemically, thermally, or photo-sensitive bond e.g., disulfidebond, UV sensitive bond, or the like. Once acrydite moieties or othermoieties comprising a labile bond are incorporated into a bead, the beadmay also comprise the labile bond. The labile bond may be, for example,useful in reversibly linking (e.g., covalently linking) species (e.g.,barcodes, primers, etc.) to a bead. In some cases, a thermally labilebond may include a nucleic acid hybridization based attachment, e.g.,where an oligonucleotide is hybridized to a complementary sequence thatis attached to the bead, such that thermal melting of the hybridreleases the oligonucleotide, e.g., a barcode containing sequence, fromthe bead or microcapsule.

The addition of multiple types of labile bonds to a gel bead may resultin the generation of a bead capable of responding to varied stimuli.Each type of labile bond may be sensitive to an associated stimulus(e.g., chemical stimulus, light, temperature, enzymatic, etc.) such thatrelease of species attached to a bead via each labile bond may becontrolled by the application of the appropriate stimulus. Suchfunctionality may be useful in controlled release of species from a gelbead. In some cases, another species comprising a labile bond may belinked to a gel bead after gel bead formation via, for example, anactivated functional group of the gel bead as described above. As willbe appreciated, barcodes that are releasably, cleavably or reversiblyattached to the beads described herein include barcodes that arereleased or releasable through cleavage of a linkage between the barcodemolecule and the bead, or that are released through degradation of theunderlying bead itself, allowing the barcodes to be accessed oraccessible by other reagents, or both.

The barcodes that are releasable as described herein may sometimes bereferred to as being activatable, in that they are available forreaction once released. Thus, for example, an activatable barcode may beactivated by releasing the barcode from a bead (or other suitable typeof partition described herein). Other activatable configurations arealso envisioned in the context of the described methods and systems.

In addition to thermally cleavable bonds, disulfide bonds and UVsensitive bonds, other non-limiting examples of labile bonds that may becoupled to a precursor or bead include an ester linkage (e.g., cleavablewith an acid, a base, or hydroxylamine), a vicinal diol linkage (e.g.,cleavable via sodium periodate), a Diels-Alder linkage (e.g., cleavablevia heat), a sulfone linkage (e.g., cleavable via a base), a silyl etherlinkage (e.g., cleavable via an acid), a glycosidic linkage (e.g.,cleavable via an amylase), a peptide linkage (e.g., cleavable via aprotease), or a phosphodiester linkage (e.g., cleavable via a nuclease(e.g., DNAase)). A bond may be cleavable via other nucleic acid moleculetargeting enzymes, such as restriction enzymes (e.g., restrictionendonucleases), as described further below.

Species may be encapsulated in beads during bead generation (e.g.,during polymerization of precursors). Such species may or may notparticipate in polymerization. Such species may be entered intopolymerization reaction mixtures such that generated beads comprise thespecies upon bead formation. In some cases, such species may be added tothe gel beads after formation. Such species may include, for example,nucleic acid molecules (e.g., oligonucleotides), reagents for a nucleicacid amplification reaction (e.g., primers, polymerases, dNTPs,co-factors (e.g., ionic co-factors), buffers) including those describedherein, reagents for enzymatic reactions (e.g., enzymes, co-factors,substrates, buffers), reagents for nucleic acid modification reactionssuch as polymerization, ligation, or digestion, and/or reagents fortemplate preparation (e.g., tagmentation) for one or more sequencingplatforms (e.g., Nextera® for Illumina®). Such species may include oneor more enzymes described herein, including without limitation,polymerase, reverse transcriptase, restriction enzymes (e.g.,endonuclease), transposase, ligase, proteinase K, DNAse, etc. Suchspecies may include one or more reagents described elsewhere herein(e.g., lysis agents, inhibitors, inactivating agents, chelating agents,stimulus). Trapping of such species may be controlled by the polymernetwork density generated during polymerization of precursors, controlof ionic charge within the gel bead (e.g., via ionic species linked topolymerized species), or by the release of other species. Encapsulatedspecies may be released from a bead upon bead degradation and/or byapplication of a stimulus capable of releasing the species from thebead. Alternatively or in addition, species may be partitioned in apartition (e.g., droplet) during or subsequent to partition formation.Such species may include, without limitation, the abovementioned speciesthat may also be encapsulated in a bead.

A degradable bead may comprise one or more species with a labile bondsuch that, when the bead/species is exposed to the appropriate stimuli,the bond is broken and the bead degrades. The labile bond may be achemical bond (e.g., covalent bond, ionic bond) or may be another typeof physical interaction (e.g., van der Waals interactions, dipole-dipoleinteractions, etc.). In some cases, a crosslinker used to generate abead may comprise a labile bond. Upon exposure to the appropriateconditions, the labile bond can be broken and the bead degraded. Forexample, upon exposure of a polyacrylamide gel bead comprising cystaminecrosslinkers to a reducing agent, the disulfide bonds of the cystaminecan be broken and the bead degraded.

A degradable bead may be useful in more quickly releasing an attachedspecies (e.g., a nucleic acid molecule, a barcode sequence, a primer,etc) from the bead when the appropriate stimulus is applied to the beadas compared to a bead that does not degrade. For example, for a speciesbound to an inner surface of a porous bead or in the case of anencapsulated species, the species may have greater mobility andaccessibility to other species in solution upon degradation of the bead.In some cases, a species may also be attached to a degradable bead via adegradable linker (e.g., disulfide linker). The degradable linker mayrespond to the same stimuli as the degradable bead or the two degradablespecies may respond to different stimuli. For example, a barcodesequence may be attached, via a disulfide bond, to a polyacrylamide beadcomprising cystamine. Upon exposure of the barcoded-bead to a reducingagent, the bead degrades and the barcode sequence is released uponbreakage of both the disulfide linkage between the barcode sequence andthe bead and the disulfide linkages of the cystamine in the bead.

As will be appreciated from the above disclosure, while referred to asdegradation of a bead, in many instances as noted above, thatdegradation may refer to the disassociation of a bound or entrainedspecies from a bead, both with and without structurally degrading thephysical bead itself. For example, entrained species may be releasedfrom beads through osmotic pressure differences due to, for example,changing chemical environments. By way of example, alteration of beadpore sizes due to osmotic pressure differences can generally occurwithout structural degradation of the bead itself. In some cases, anincrease in pore size due to osmotic swelling of a bead can permit therelease of entrained species within the bead. In other cases, osmoticshrinking of a bead may cause a bead to better retain an entrainedspecies due to pore size contraction.

Where degradable beads are provided, it may be beneficial to avoidexposing such beads to the stimulus or stimuli that cause suchdegradation prior to a given time, in order to, for example, avoidpremature bead degradation and issues that arise from such degradation,including for example poor flow characteristics and aggregation. By wayof example, where beads comprise reducible cross-linking groups, such asdisulfide groups, it will be desirable to avoid contacting such beadswith reducing agents, e.g., DTT or other disulfide cleaving reagents. Insuch cases, treatment to the beads described herein will, in some casesbe provided free of reducing agents, such as DTT. Because reducingagents are often provided in commercial enzyme preparations, it may bedesirable to provide reducing agent free (or DTT free) enzymepreparations in treating the beads described herein. Examples of suchenzymes include, e.g., polymerase enzyme preparations, reversetranscriptase enzyme preparations, ligase enzyme preparations, as wellas many other enzyme preparations that may be used to treat the beadsdescribed herein. The terms “reducing agent free” or “DTT free”preparations can refer to a preparation having less than about 1/10th,less than about 1/50th, or even less than about 1/100th of the lowerranges for such materials used in degrading the beads. For example, forDTT, the reducing agent free preparation can have less than about 0.01millimolar (mM), 0.005 mM, 0.001 mM DTT, 0.0005 mM DTT, or even lessthan about 0.0001 mM DTT. In many cases, the amount of DTT can beundetectable.

Numerous chemical triggers may be used to trigger the degradation ofbeads. Examples of these chemical changes may include, but are notlimited to pH-mediated changes to the integrity of a component withinthe bead, degradation of a component of a bead via cleavage ofcross-linked bonds, and depolymerization of a component of a bead.

In some embodiments, a bead may be formed from materials that comprisedegradable chemical crosslinkers, such as BAC or cystamine. Degradationof such degradable crosslinkers may be accomplished through a number ofmechanisms. In some examples, a bead may be contacted with a chemicaldegrading agent that may induce oxidation, reduction or other chemicalchanges. For example, a chemical degrading agent may be a reducingagent, such as dithiothreitol (DTT). Additional examples of reducingagents may include β-mercaptoethanol, (2S)-2-amino-1,4-dimercaptobutane(dithiobutylamine or DTBA), tris(2-carboxyethyl) phosphine (TCEP), orcombinations thereof. A reducing agent may degrade the disulfide bondsformed between gel precursors forming the bead, and thus, degrade thebead. In other cases, a change in pH of a solution, such as an increasein pH, may trigger degradation of a bead. In other cases, exposure to anaqueous solution, such as water, may trigger hydrolytic degradation, andthus degradation of the bead. In some cases, any combination of stimulimay trigger degradation of a bead. For example, a change in pH mayenable a chemical agent (e.g., DTT) to become an effective reducingagent.

Beads may also be induced to release their contents upon the applicationof a thermal stimulus. A change in temperature can cause a variety ofchanges to a bead. For example, heat can cause a solid bead to liquefy.A change in heat may cause melting of a bead such that a portion of thebead degrades. In other cases, heat may increase the internal pressureof the bead components such that the bead ruptures or explodes. Heat mayalso act upon heat-sensitive polymers used as materials to constructbeads.

Any suitable agent may degrade beads. In some embodiments, changes intemperature or pH may be used to degrade thermo-sensitive orpH-sensitive bonds within beads. In some embodiments, chemical degradingagents may be used to degrade chemical bonds within beads by oxidation,reduction or other chemical changes. For example, a chemical degradingagent may be a reducing agent, such as DTT, wherein DTT may degrade thedisulfide bonds formed between a crosslinker and gel precursors, thusdegrading the bead. In some embodiments, a reducing agent may be addedto degrade the bead, which may or may not cause the bead to release itscontents. Examples of reducing agents may include dithiothreitol (DTT),β-mercaptoethanol, (2S)-2-amino-1,4-dimercaptobutane (dithiobutylamineor DTBA), tris(2-carboxyethyl) phosphine (TCEP), or combinationsthereof. The reducing agent may be present at a concentration of about0.1 mM, 0.5 mM, 1 mM, 5 mM, 10 mM. The reducing agent may be present ata concentration of at least about 0.1 mM, 0.5 mM, 1 mM, 5 mM, 10 mM, orgreater than 10 mM. The reducing agent may be present at concentrationof at most about 10 mM, 5 mM, 1 mM, 0.5 mM, 0.1 mM, or less.

Any suitable number of molecular tag molecules (e.g., primer, barcodedoligonucleotide) can be associated with a bead such that, upon releasefrom the bead, the molecular tag molecules (e.g., primer, e.g., barcodedoligonucleotide) are present in the partition at a pre-definedconcentration. Such pre-defined concentration may be selected tofacilitate certain reactions for generating a sequencing library, e.g.,amplification, within the partition. In some cases, the pre-definedconcentration of the primer can be limited by the process of producingoligonucleotide bearing beads.

Although FIG. 1 and FIG. 2 have been described in terms of providingsubstantially singly occupied partitions, above, in certain cases, itmay be desirable to provide multiply occupied partitions, e.g.,containing two, three, four or more cells and/or microcapsules (e.g.,beads) comprising barcoded nucleic acid molecules (e.g.,oligonucleotides) within a single partition. Accordingly, as notedabove, the flow characteristics of the biological particle and/or beadcontaining fluids and partitioning fluids may be controlled to providefor such multiply occupied partitions. In particular, the flowparameters may be controlled to provide a given occupancy rate atgreater than about 50% of the partitions, greater than about 75%, and insome cases greater than about 80%, 90%, 95%, or higher.

In some cases, additional microcapsules can be used to deliveradditional reagents to a partition. In such cases, it may beadvantageous to introduce different beads into a common channel ordroplet generation junction, from different bead sources (e.g.,containing different associated reagents) through different channelinlets into such common channel or droplet generation junction (e.g.,junction 210). In such cases, the flow and frequency of the differentbeads into the channel or junction may be controlled to provide for acertain ratio of microcapsules from each source, while ensuring a givenpairing or combination of such beads into a partition with a givennumber of biological particles (e.g., one biological particle and onebead per partition).

The partitions described herein may comprise small volumes, for example,less than about 10 microliters (4), 54, 14, 900 picoliters (pL), 800 pL,700 pL, 600 pL, 500 pL, 400 pL, 300 pL, 200 pL, 100 pL, 50 pL, 20 pL, 10pL, 1 pL, 500 nanoliters (nL), 100 nL, 50 nL, or less.

For example, in the case of droplet based partitions, the droplets mayhave overall volumes that are less than about 1000 pL, 900 pL, 800 pL,700 pL, 600 pL, 500 pL, 400pL, 300 pL, 200 pL, 100pL, 50 pL, 20 pL, 10pL, 1 pL, or less. Where co-partitioned with microcapsules, it will beappreciated that the sample fluid volume, e.g., including co-partitionedbiological particles and/or beads, within the partitions may be lessthan about 90% of the above described volumes, less than about 80%, lessthan about 70%, less than about 60%, less than about 50%, less thanabout 40%, less than about 30%, less than about 20%, or less than about10% of the above described volumes.

As is described elsewhere herein, partitioning species may generate apopulation or plurality of partitions. In such cases, any suitablenumber of partitions can be generated or otherwise provided. Forexample, at least about 1,000 partitions, at least about 5,000partitions, at least about 10,000 partitions, at least about 50,000partitions, at least about 100,000 partitions, at least about 500,000partitions, at least about 1,000,000 partitions, at least about5,000,000 partitions at least about 10,000,000 partitions, at leastabout 50,000,000 partitions, at least about 100,000,000 partitions, atleast about 500,000,000 partitions, at least about 1,000,000,000partitions, or more partitions can be generated or otherwise provided.Moreover, the plurality of partitions may comprise both unoccupiedpartitions (e.g., empty partitions) and occupied partitions.

Reagents

In accordance with certain aspects, biological particles may bepartitioned along with lysis reagents in order to release the contentsof the biological particles within the partition. In such cases, thelysis agents can be contacted with the biological particle suspensionconcurrently with, or immediately prior to, the introduction of thebiological particles into the partitioning junction/droplet generationzone (e.g., junction 210), such as through an additional channel orchannels upstream of the channel junction. In accordance with otheraspects, additionally or alternatively, biological particles may bepartitioned along with other reagents, as will be described furtherbelow.

FIG. 3 shows an example of a microfluidic channel structure 300 forco-partitioning biological particles and reagents. The channel structure300 can include channel segments 301, 302, 304, 306 and 308. Channelsegments 301 and 302 communicate at a first channel junction 309.Channel segments 302, 304, 306, and 308 communicate at a second channeljunction 310.

In an example operation, the channel segment 301 may transport anaqueous fluid 312 that includes a plurality of biological particles 314along the channel segment 301 into the second junction 310. As analternative or in addition to, channel segment 301 may transport beads(e.g., gel beads). The beads may comprise barcode molecules.

For example, the channel segment 301 may be connected to a reservoircomprising an aqueous suspension of biological particles 314. Upstreamof, and immediately prior to reaching, the second junction 310, thechannel segment 301 may meet the channel segment 302 at the firstjunction 309. The channel segment 302 may transport a plurality ofreagents 315 (e.g., lysis agents) suspended in the aqueous fluid 312along the channel segment 302 into the first junction 309. For example,the channel segment 302 may be connected to a reservoir comprising thereagents 315. After the first junction 309, the aqueous fluid 312 in thechannel segment 301 can carry both the biological particles 314 and thereagents 315 towards the second junction 310. In some instances, theaqueous fluid 312 in the channel segment 301 can include one or morereagents, which can be the same or different reagents as the reagents315. A second fluid 316 that is immiscible with the aqueous fluid 312(e.g., oil) can be delivered to the second junction 310 from each ofchannel segments 304 and 306. Upon meeting of the aqueous fluid 312 fromthe channel segment 301 and the second fluid 316 from each of channelsegments 304 and 306 at the second channel junction 310, the aqueousfluid 312 can be partitioned as discrete droplets 318 in the secondfluid 316 and flow away from the second junction 310 along channelsegment 308. The channel segment 308 may deliver the discrete droplets318 to an outlet reservoir fluidly coupled to the channel segment 308,where they may be harvested.

The second fluid 316 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resulting droplets318.

A discrete droplet generated may include an individual biologicalparticle 314 and/or one or more reagents 315. In some instances, adiscrete droplet generated may include a barcode carrying bead (notshown), such as via other microfluidics structures described elsewhereherein. In some instances, a discrete droplet may be unoccupied (e.g.,no reagents, no biological particles).

Beneficially, when lysis reagents and biological particles areco-partitioned, the lysis reagents can facilitate the release of thecontents of the biological particles within the partition. The contentsreleased in a partition may remain discrete from the contents of otherpartitions.

As will be appreciated, the channel segments described herein may becoupled to any of a variety of different fluid sources or receivingcomponents, including reservoirs, tubing, manifolds, or fluidiccomponents of other systems. As will be appreciated, the microfluidicchannel structure 300 may have other geometries. For example, amicrofluidic channel structure can have more than two channel junctions.For example, a microfluidic channel structure can have 2, 3, 4, 5channel segments or more each carrying the same or different types ofbeads, reagents, and/or biological particles that meet at a channeljunction. Fluid flow in each channel segment may be controlled tocontrol the partitioning of the different elements into droplets. Fluidmay be directed flow along one or more channels or reservoirs via one ormore fluid flow units. A fluid flow unit can comprise compressors (e.g.,providing positive pressure), pumps (e.g., providing negative pressure),actuators, and the like to control flow of the fluid. Fluid may also orotherwise be controlled via applied pressure differentials, centrifugalforce, electrokinetic pumping, vacuum, capillary or gravity flow, or thelike.

Examples of lysis agents include bioactive reagents, such as lysisenzymes that are used for lysis of different cell types, e.g., grampositive or negative bacteria, plants, yeast, mammalian, etc., such aslysozymes, achromopeptidase, lysostaphin, labiase, kitalase, lyticase,and a variety of other lysis enzymes available from, e.g.,Sigma-Aldrich, Inc. (St Louis, Mo.), as well as other commerciallyavailable lysis enzymes. Other lysis agents may additionally oralternatively be co-partitioned with the biological particles to causethe release of the biological particles's contents into the partitions.For example, in some cases, surfactant-based lysis solutions may be usedto lyse cells, although these may be less desirable for emulsion basedsystems where the surfactants can interfere with stable emulsions. Insome cases, lysis solutions may include non-ionic surfactants such as,for example, TritonX-100 and Tween 20. In some cases, lysis solutionsmay include ionic surfactants such as, for example, sarcosyl and sodiumdodecyl sulfate (SDS). Electroporation, thermal, acoustic or mechanicalcellular disruption may also be used in certain cases, e.g.,non-emulsion based partitioning such as encapsulation of biologicalparticles that may be in addition to or in place of dropletpartitioning, where any pore size of the encapsulate is sufficientlysmall to retain nucleic acid fragments of a given size, followingcellular disruption.

Alternatively or in addition to the lysis agents co-partitioned with thebiological particles described above, other reagents can also beco-partitioned with the biological particles, including, for example,DNase and RNase inactivating agents or inhibitors, such as proteinase K,chelating agents, such as EDTA, and other reagents employed in removingor otherwise reducing negative activity or impact of different celllysate components on subsequent processing of nucleic acids. Inaddition, in the case of encapsulated biological particles, thebiological particles may be exposed to an appropriate stimulus torelease the biological particles or their contents from a co-partitionedmicrocapsule. For example, in some cases, a chemical stimulus may beco-partitioned along with an encapsulated biological particle to allowfor the degradation of the microcapsule and release of the cell or itscontents into the larger partition. In some cases, this stimulus may bethe same as the stimulus described elsewhere herein for release ofnucleic acid molecules (e.g., oligonucleotides) from their respectivemicrocapsule (e.g., bead). In alternative aspects, this may be adifferent and non-overlapping stimulus, in order to allow anencapsulated biological particle to be released into a partition at adifferent time from the release of nucleic acid molecules into the samepartition.

Additional reagents may also be co-partitioned with the biologicalparticles, such as endonucleases to fragment a biological particle'sDNA, DNA polymerase enzymes and dNTPs used to amplify the biologicalparticle's nucleic acid fragments and to attach the barcode moleculartags to the amplified fragments. Other enzymes may be co-partitioned,including without limitation, polymerase, transposase, ligase,proteinase K, DNAse, etc. Additional reagents may also include reversetranscriptase enzymes, including enzymes with terminal transferaseactivity, primers and oligonucleotides, and switch oligonucleotides(also referred to herein as “switch oligos” or “template switchingoligonucleotides”) which can be used for template switching. In somecases, template switching can be used to increase the length of a cDNA.In some cases, template switching can be used to append a predefinednucleic acid sequence to the cDNA. In an example of template switching,cDNA can be generated from reverse transcription of a template, e.g.,cellular mRNA, where a reverse transcriptase with terminal transferaseactivity can add additional nucleotides, e.g., polyC, to the cDNA in atemplate independent manner. Switch oligos can include sequencescomplementary to the additional nucleotides, e.g., polyG. The additionalnucleotides (e.g., polyC) on the cDNA can hybridize to the additionalnucleotides (e.g., polyG) on the switch oligo, whereby the switch oligocan be used by the reverse transcriptase as template to further extendthe cDNA. Template switching oligonucleotides may comprise ahybridization region and a template region. The hybridization region cancomprise any sequence capable of hybridizing to the target. In somecases, as previously described, the hybridization region comprises aseries of G bases to complement the overhanging C bases at the 3′ end ofa cDNA molecule. The series of G bases may comprise 1 G base, 2 G bases,3 G bases, 4 G bases, 5 G bases or more than 5 G bases. The templatesequence can comprise any sequence to be incorporated into the cDNA. Insome cases, the template region comprises at least 1 (e.g., at least 2,3, 4, 5 or more) tag sequences and/or functional sequences. Switcholigos may comprise deoxyribonucleic acids; ribonucleic acids; modifiednucleic acids including 2-Aminopurine, 2,6-Diaminopurine (2-Amino-dA),inverted dT, 5-Methyl dC, 2′-deoxylnosine, Super T(5-hydroxybutynl-2′-deoxyuridine), Super G (8-aza-7-deazaguanosine),locked nucleic acids (LNAs), unlocked nucleic acids (UNAs, e.g., UNA-A,UNA-U, UNA-C, UNA-G), Iso-dG, Iso-dC, 2′ Fluoro bases (e.g., Fluoro C,Fluoro U, Fluoro A, and Fluoro G), or any combination.

In some cases, the length of a switch oligo may be at least about 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76,77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94,95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109,110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151,152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165,166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193,194, 195, 196, 197 , 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221,222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235,236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249 or250 nucleotides or longer.

In some cases, the length of a switch oligo may be at most about 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76,77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94,95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109,110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123,124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151,152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165,166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193,194, 195, 196, 197 , 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221,222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235,236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249 or250 nucleotides.

Once the contents of the cells are released into their respectivepartitions, the macromolecular components (e.g., macromolecularconstituents of biological particles, such as RNA, DNA, or proteins)contained therein may be further processed within the partitions. Inaccordance with the methods and systems described herein, themacromolecular component contents of individual biological particles canbe provided with unique identifiers such that, upon characterization ofthose macromolecular components they may be attributed as having beenderived from the same biological particle or particles. The ability toattribute characteristics to individual biological particles or groupsof biological particles is provided by the assignment of uniqueidentifiers specifically to an individual biological particle or groupsof biological particles. Unique identifiers, e.g., in the form ofnucleic acid barcodes can be assigned or associated with individualbiological particles or populations of biological particles, in order totag or label the biological particle's macromolecular components (and asa result, its characteristics) with the unique identifiers. These uniqueidentifiers can then be used to attribute the biological particle'scomponents and characteristics to an individual biological particle orgroup of biological particles.

In some aspects, this is performed by co-partitioning the individualbiological particle or groups of biological particles with the uniqueidentifiers, such as described above (with reference to FIG. 2). In someaspects, the unique identifiers are provided in the form of nucleic acidmolecules (e.g., oligonucleotides) that comprise nucleic acid barcodesequences that may be attached to or otherwise associated with thenucleic acid contents of individual biological particle, or to othercomponents of the biological particle, and particularly to fragments ofthose nucleic acids. The nucleic acid molecules are partitioned suchthat as between nucleic acid molecules in a given partition, the nucleicacid barcode sequences contained therein are the same, but as betweendifferent partitions, the nucleic acid molecule can, and do havediffering barcode sequences, or at least represent a large number ofdifferent barcode sequences across all of the partitions in a givenanalysis. In some aspects, only one nucleic acid barcode sequence can beassociated with a given partition, although in some cases, two or moredifferent barcode sequences may be present.

The nucleic acid barcode sequences can include from about 6 to about 20or more nucleotides within the sequence of the nucleic acid molecules(e.g., oligonucleotides). The nucleic acid barcode sequences can includefrom about 6 to about 20, 30, 40, 50, 60, 70, 80, 90, 100 or morenucleotides. In some cases, the length of a barcode sequence may beabout 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotidesor longer. In some cases, the length of a barcode sequence may be atleast about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20nucleotides or longer. In some cases, the length of a barcode sequencemay be at most about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20 nucleotides or shorter. These nucleotides may be completelycontiguous, i.e., in a single stretch of adjacent nucleotides, or theymay be separated into two or more separate subsequences that areseparated by 1 or more nucleotides. In some cases, separated barcodesubsequences can be from about 4 to about 16 nucleotides in length. Insome cases, the barcode subsequence may be about 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16 nucleotides or longer. In some cases, the barcodesubsequence may be at least about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16 nucleotides or longer. In some cases, the barcode subsequence maybe at most about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16nucleotides or shorter.

The co-partitioned nucleic acid molecules can also comprise otherfunctional sequences useful in the processing of the nucleic acids fromthe co-partitioned biological particles. These sequences include, e.g.,targeted or random/universal amplification primer sequences foramplifying the genomic DNA from the individual biological particleswithin the partitions while attaching the associated barcode sequences,sequencing primers or primer recognition sites, hybridization or probingsequences, e.g., for identification of presence of the sequences or forpulling down barcoded nucleic acids, or any of a number of otherpotential functional sequences. Other mechanisms of co-partitioningoligonucleotides may also be employed, including, e.g., coalescence oftwo or more droplets, where one droplet contains oligonucleotides, ormicrodispensing of oligonucleotides into partitions, e.g., dropletswithin microfluidic systems.

In an example, microcapsules, such as beads, are provided that eachinclude large numbers of the above described barcoded nucleic acidmolecules (e.g., barcoded oligonucleotides) releasably attached to thebeads, where all of the nucleic acid molecules attached to a particularbead will include the same nucleic acid barcode sequence, but where alarge number of diverse barcode sequences are represented across thepopulation of beads used. In some embodiments, hydrogel beads, e.g.,comprising polyacrylamide polymer matrices, are used as a solid supportand delivery vehicle for the nucleic acid molecules into the partitions,as they are capable of carrying large numbers of nucleic acid molecules,and may be configured to release those nucleic acid molecules uponexposure to a particular stimulus, as described elsewhere herein. Insome cases, the population of beads provides a diverse barcode sequencelibrary that includes at least about 1,000 different barcode sequences,at least about 5,000 different barcode sequences, at least about 10,000different barcode sequences, at least about 50,000 different barcodesequences, at least about 100,000 different barcode sequences, at leastabout 1,000,000 different barcode sequences, at least about 5,000,000different barcode sequences, or at least about 10,000,000 differentbarcode sequences, or more. Additionally, each bead can be provided withlarge numbers of nucleic acid (e.g., oligonucleotide) moleculesattached. In particular, the number of molecules of nucleic acidmolecules including the barcode sequence on an individual bead can be atleast about 1,000 nucleic acid molecules, at least about 5,000 nucleicacid molecules, at least about 10,000 nucleic acid molecules, at leastabout 50,000 nucleic acid molecules, at least about 100,000 nucleic acidmolecules, at least about 500,000 nucleic acids, at least about1,000,000 nucleic acid molecules, at least about 5,000,000 nucleic acidmolecules, at least about 10,000,000 nucleic acid molecules, at leastabout 50,000,000 nucleic acid molecules, at least about 100,000,000nucleic acid molecules, at least about 250,000,000 nucleic acidmolecules and in some cases at least about 1 billion nucleic acidmolecules, or more. Nucleic acid molecules of a given bead can includeidentical (or common) barcode sequences, different barcode sequences, ora combination of both. Nucleic acid molecules of a given bead caninclude multiple sets of nucleic acid molecules. Nucleic acid moleculesof a given set can include identical barcode sequences. The identicalbarcode sequences can be different from barcode sequences of nucleicacid molecules of another set.

Moreover, when the population of beads is partitioned, the resultingpopulation of partitions can also include a diverse barcode library thatincludes at least about 1,000 different barcode sequences, at leastabout 5,000 different barcode sequences, at least about 10,000 differentbarcode sequences, at least at least about 50,000 different barcodesequences, at least about 100,000 different barcode sequences, at leastabout 1,000,000 different barcode sequences, at least about 5,000,000different barcode sequences, or at least about 10,000,000 differentbarcode sequences. Additionally, each partition of the population caninclude at least about 1,000 nucleic acid molecules, at least about5,000 nucleic acid molecules, at least about 10,000 nucleic acidmolecules, at least about 50,000 nucleic acid molecules, at least about100,000 nucleic acid molecules, at least about 500,000 nucleic acids, atleast about 1,000,000 nucleic acid molecules, at least about 5,000,000nucleic acid molecules, at least about 10,000,000 nucleic acidmolecules, at least about 50,000,000 nucleic acid molecules, at leastabout 100,000,000 nucleic acid molecules, at least about 250,000,000nucleic acid molecules and in some cases at least about 1 billionnucleic acid molecules.

In some cases, it may be desirable to incorporate multiple differentbarcodes within a given partition, either attached to a single ormultiple beads within the partition. For example, in some cases, amixed, but known set of barcode sequences may provide greater assuranceof identification in the subsequent processing, e.g., by providing astronger address or attribution of the barcodes to a given partition, asa duplicate or independent confirmation of the output from a givenpartition.

The nucleic acid molecules (e.g., oligonucleotides) are releasable fromthe beads upon the application of a particular stimulus to the beads. Insome cases, the stimulus may be a photo-stimulus, e.g., through cleavageof a photo-labile linkage that releases the nucleic acid molecules. Inother cases, a thermal stimulus may be used, where elevation of thetemperature of the beads environment will result in cleavage of alinkage or other release of the nucleic acid molecules form the beads.In still other cases, a chemical stimulus can be used that cleaves alinkage of the nucleic acid molecules to the beads, or otherwise resultsin release of the nucleic acid molecules from the beads. In one case,such compositions include the polyacrylamide matrices described abovefor encapsulation of biological particles, and may be degraded forrelease of the attached nucleic acid molecules through exposure to areducing agent, such as DTT.

In some aspects, provided are systems and methods for controlledpartitioning. Droplet size may be controlled by adjusting certaingeometric features in channel architecture (e.g., microfluidics channelarchitecture). For example, an expansion angle, width, and/or length ofa channel may be adjusted to control droplet size.

FIG. 4 shows an example of a microfluidic channel structure for thecontrolled partitioning of beads into discrete droplets. A channelstructure 400 can include a channel segment 402 communicating at achannel junction 406 (or intersection) with a reservoir 404. Thereservoir 404 can be a chamber. Any reference to “reservoir,” as usedherein, can also refer to a “chamber.” In operation, an aqueous fluid408 that includes suspended beads 412 may be transported along thechannel segment 402 into the junction 406 to meet a second fluid 410that is immiscible with the aqueous fluid 408 in the reservoir 404 tocreate droplets 416, 418 of the aqueous fluid 408 flowing into thereservoir 404. At the junction 406 where the aqueous fluid 408 and thesecond fluid 410 meet, droplets can form based on factors such as thehydrodynamic forces at the junction 406, flow rates of the two fluids408, 410, fluid properties, and certain geometric parameters (e.g., w,ho, a, etc.) of the channel structure 400. A plurality of droplets canbe collected in the reservoir 404 by continuously injecting the aqueousfluid 408 from the channel segment 402 through the junction 406.

A discrete droplet generated may include a bead (e.g., as in occupieddroplets 416). Alternatively, a discrete droplet generated may includemore than one bead. Alternatively, a discrete droplet generated may notinclude any beads (e.g., as in unoccupied droplet 418). In someinstances, a discrete droplet generated may contain one or morebiological particles, as described elsewhere herein. In some instances,a discrete droplet generated may comprise one or more reagents, asdescribed elsewhere herein.

In some instances, the aqueous fluid 408 can have a substantiallyuniform concentration or frequency of beads 412. The beads 412 can beintroduced into the channel segment 402 from a separate channel (notshown in FIG. 4). The frequency of beads 412 in the channel segment 402may be controlled by controlling the frequency in which the beads 412are introduced into the channel segment 402 and/or the relative flowrates of the fluids in the channel segment 402 and the separate channel.In some instances, the beads can be introduced into the channel segment402 from a plurality of different channels, and the frequency controlledaccordingly.

In some instances, the aqueous fluid 408 in the channel segment 402 cancomprise biological particles (e.g., described with reference to FIGS. 1and 2). In some instances, the aqueous fluid 408 can have asubstantially uniform concentration or frequency of biologicalparticles. As with the beads, the biological particles can be introducedinto the channel segment 402 from a separate channel. The frequency orconcentration of the biological particles in the aqueous fluid 408 inthe channel segment 402 may be controlled by controlling the frequencyin which the biological particles are introduced into the channelsegment 402 and/or the relative flow rates of the fluids in the channelsegment 402 and the separate channel. In some instances, the biologicalparticles can be introduced into the channel segment 402 from aplurality of different channels, and the frequency controlledaccordingly. In some instances, a first separate channel can introducebeads and a second separate channel can introduce biological particlesinto the channel segment 402. The first separate channel introducing thebeads may be upstream or downstream of the second separate channelintroducing the biological particles.

The second fluid 410 can comprise an oil, such as a fluorinated oil,that includes a fluorosurfactant for stabilizing the resulting droplets,for example, inhibiting subsequent coalescence of the resultingdroplets.

In some instances, the second fluid 410 may not be subjected to and/ordirected to any flow in or out of the reservoir 404. For example, thesecond fluid 410 may be substantially stationary in the reservoir 404.In some instances, the second fluid 410 may be subjected to flow withinthe reservoir 404, but not in or out of the reservoir 404, such as viaapplication of pressure to the reservoir 404 and/or as affected by theincoming flow of the aqueous fluid 408 at the junction 406.Alternatively, the second fluid 410 may be subjected and/or directed toflow in or out of the reservoir 404. For example, the reservoir 404 canbe a channel directing the second fluid 410 from upstream to downstream,transporting the generated droplets.

The channel structure 400 at or near the junction 406 may have certaingeometric features that at least partly determine the sizes of thedroplets formed by the channel structure 400. The channel segment 402can have a height, ho and width, w, at or near the junction 406. By wayof example, the channel segment 402 can comprise a rectangularcross-section that leads to a reservoir 404 having a wider cross-section(such as in width or diameter). Alternatively, the cross-section of thechannel segment 402 can be other shapes, such as a circular shape,trapezoidal shape, polygonal shape, or any other shapes. The top andbottom walls of the reservoir 404 at or near the junction 406 can beinclined at an expansion angle, a. The expansion angle, a, allows thetongue (portion of the aqueous fluid 408 leaving channel segment 402 atjunction 406 and entering the reservoir 404 before droplet formation) toincrease in depth and facilitate decrease in curvature of theintermediately formed droplet. Droplet size may decrease with increasingexpansion angle. The resulting droplet radius, R_(d), may be predictedby the following equation for the aforementioned geometric parameters ofh₀, w, and α:

$R_{d} \approx {0.44( {1 + {2.2\sqrt{\tan\alpha}\frac{w}{h_{0}}}} )\frac{h_{0}}{\sqrt{\tan\alpha}}}$

By way of example, for a channel structure with w=21 μm, h=21 μm, andα=3°, the predicted droplet size is 121 μm. In another example, for achannel structure with w=25 μm, h=25 μm, and α=5°, the predicted dropletsize is 123 μm. In another example, for a channel structure with w=28μm, h=28 μm, and α=7°, the predicted droplet size is 124 μm.

In some instances, the expansion angle, a, may be between a range offrom about 0.5° to about 4°, from about 0.1° to about 10°, or from about0° to about 90°. For example, the expansion angle can be at least about0.01°, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°,4°, 5°, 6°, 7°, 8°, 9°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°,55°, 60°, 65°, 70°, 75°, 80°, 85°, or higher. In some instances, theexpansion angle can be at most about 89°, 88°, 87°, 86°, 85°, 84°, 83°,82°, 81°, 80°, 75°, 70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°,20°, 15°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, 1°, 0.1°, 0.01°, or less.In some instances, the width, w, can be between a range of from about100 micrometers (μm) to about 500 μm. In some instances, the width, w,can be between a range of from about 10 μm to about 200 μm.Alternatively, the width can be less than about 10 μm. Alternatively,the width can be greater than about 500 μm. In some instances, the flowrate of the aqueous fluid 408 entering the junction 406 can be betweenabout 0.04 microliters (μL)/minute (min) and about 40 μL/min. In someinstances, the flow rate of the aqueous fluid 408 entering the junction406 can be between about 0.01 microliters (μL)/minute (min) and about100 μL/min. Alternatively, the flow rate of the aqueous fluid 408entering the junction 406 can be less than about 0.01 μL/min.Alternatively, the flow rate of the aqueous fluid 408 entering thejunction 406 can be greater than about 40 μL/min, such as 45 μL/min, 50μL/min, 55 μL/min, 60 μL/min, 65 μL/min, 70 μL/min, 75 μL/min, 80μL/min, 85 μL/min, 90 μL/min, 95 μL/min, 100 μL/min, 110 μL/min , 120μL/min , 130 μL/min, 140 μL/min , 150 μL/min, or greater. At lower flowrates, such as flow rates of about less than or equal to 10microliters/minute, the droplet radius may not be dependent on the flowrate of the aqueous fluid 408 entering the junction 406.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

The throughput of droplet generation can be increased by increasing thepoints of generation, such as increasing the number of junctions (e.g.,junction 406) between aqueous fluid 408 channel segments (e.g., channelsegment 402) and the reservoir 404. Alternatively or in addition, thethroughput of droplet generation can be increased by increasing the flowrate of the aqueous fluid 408 in the channel segment 402.

FIG. 5 shows an example of a microfluidic channel structure forincreased droplet generation throughput. A microfluidic channelstructure 500 can comprise a plurality of channel segments 502 and areservoir 504. Each of the plurality of channel segments 502 may be influid communication with the reservoir 504. The channel structure 500can comprise a plurality of channel junctions 506 between the pluralityof channel segments 502 and the reservoir 504. Each channel junction canbe a point of droplet generation. The channel segment 402 from thechannel structure 400 in FIG. 4 and any description to the componentsthereof may correspond to a given channel segment of the plurality ofchannel segments 502 in channel structure 500 and any description to thecorresponding components thereof. The reservoir 404 from the channelstructure 400 and any description to the components thereof maycorrespond to the reservoir 504 from the channel structure 500 and anydescription to the corresponding components thereof

Each channel segment of the plurality of channel segments 502 maycomprise an aqueous fluid 508 that includes suspended beads 512. Thereservoir 504 may comprise a second fluid 510 that is immiscible withthe aqueous fluid 508. In some instances, the second fluid 510 may notbe subjected to and/or directed to any flow in or out of the reservoir504. For example, the second fluid 510 may be substantially stationaryin the reservoir 504. In some instances, the second fluid 510 may besubjected to flow within the reservoir 504, but not in or out of thereservoir 504, such as via application of pressure to the reservoir 504and/or as affected by the incoming flow of the aqueous fluid 508 at thejunctions. Alternatively, the second fluid 510 may be subjected and/ordirected to flow in or out of the reservoir 504. For example, thereservoir 504 can be a channel directing the second fluid 510 fromupstream to downstream, transporting the generated droplets.

In operation, the aqueous fluid 508 that includes suspended beads 512may be transported along the plurality of channel segments 502 into theplurality of junctions 506 to meet the second fluid 510 in the reservoir504 to create droplets 516, 518. A droplet may form from each channelsegment at each corresponding junction with the reservoir 504. At thejunction where the aqueous fluid 508 and the second fluid 510 meet,droplets can form based on factors such as the hydrodynamic forces atthe junction, flow rates of the two fluids 508, 510, fluid properties,and certain geometric parameters (e.g., w, h₀, α, etc.) of the channelstructure 500, as described elsewhere herein. A plurality of dropletscan be collected in the reservoir 504 by continuously injecting theaqueous fluid 508 from the plurality of channel segments 502 through theplurality of junctions 506. Throughput may significantly increase withthe parallel channel configuration of channel structure 500. Forexample, a channel structure having five inlet channel segmentscomprising the aqueous fluid 508 may generate droplets five times asfrequently than a channel structure having one inlet channel segment,provided that the fluid flow rate in the channel segments aresubstantially the same. The fluid flow rate in the different inletchannel segments may or may not be substantially the same. A channelstructure may have as many parallel channel segments as is practical andallowed for the size of the reservoir. For example, the channelstructure may have at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 150, 500, 250, 300, 350, 400, 450, 500,600, 700, 800, 900, 1000, 1500, 5000 or more parallel or substantiallyparallel channel segments.

The geometric parameters, w, ho, and a, may or may not be uniform foreach of the channel segments in the plurality of channel segments 502.For example, each channel segment may have the same or different widthsat or near its respective channel junction with the reservoir 504. Forexample, each channel segment may have the same or different height ator near its respective channel junction with the reservoir 504. Inanother example, the reservoir 504 may have the same or differentexpansion angle at the different channel junctions with the plurality ofchannel segments 502. When the geometric parameters are uniform,beneficially, droplet size may also be controlled to be uniform evenwith the increased throughput. In some instances, when it is desirableto have a different distribution of droplet sizes, the geometricparameters for the plurality of channel segments 502 may be variedaccordingly.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

FIG. 6 shows another example of a microfluidic channel structure forincreased droplet generation throughput. A microfluidic channelstructure 600 can comprise a plurality of channel segments 602 arrangedgenerally circularly around the perimeter of a reservoir 604. Each ofthe plurality of channel segments 602 may be in fluid communication withthe reservoir 604. The channel structure 600 can comprise a plurality ofchannel junctions 606 between the plurality of channel segments 602 andthe reservoir 604. Each channel junction can be a point of dropletgeneration. The channel segment 402 from the channel structure 400 inFIG. 2 and any description to the components thereof may correspond to agiven channel segment of the plurality of channel segments 602 inchannel structure 600 and any description to the correspondingcomponents thereof. The reservoir 404 from the channel structure 400 andany description to the components thereof may correspond to thereservoir 604 from the channel structure 600 and any description to thecorresponding components thereof

Each channel segment of the plurality of channel segments 602 maycomprise an aqueous fluid 608 that includes suspended beads 612. Thereservoir 604 may comprise a second fluid 610 that is immiscible withthe aqueous fluid 608. In some instances, the second fluid 610 may notbe subjected to and/or directed to any flow in or out of the reservoir604. For example, the second fluid 610 may be substantially stationaryin the reservoir 604. In some instances, the second fluid 610 may besubjected to flow within the reservoir 604, but not in or out of thereservoir 604, such as via application of pressure to the reservoir 604and/or as affected by the incoming flow of the aqueous fluid 608 at thejunctions. Alternatively, the second fluid 610 may be subjected and/ordirected to flow in or out of the reservoir 604. For example, thereservoir 604 can be a channel directing the second fluid 610 fromupstream to downstream, transporting the generated droplets.

In operation, the aqueous fluid 608 that includes suspended beads 612may be transported along the plurality of channel segments 602 into theplurality of junctions 606 to meet the second fluid 610 in the reservoir604 to create a plurality of droplets 616. A droplet may form from eachchannel segment at each corresponding junction with the reservoir 604.At the junction where the aqueous fluid 608 and the second fluid 610meet, droplets can form based on factors such as the hydrodynamic forcesat the junction, flow rates of the two fluids 608, 610, fluidproperties, and certain geometric parameters (e.g., widths and heightsof the channel segments 602, expansion angle of the reservoir 604, etc.)of the channel structure 600, as described elsewhere herein. A pluralityof droplets can be collected in the reservoir 604 by continuouslyinjecting the aqueous fluid 608 from the plurality of channel segments602 through the plurality of junctions 606. Throughput may significantlyincrease with the substantially parallel channel configuration of thechannel structure 600. A channel structure may have as manysubstantially parallel channel segments as is practical and allowed forby the size of the reservoir. For example, the channel structure mayhave at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900,1000, 1500, 5000 or more parallel or substantially parallel channelsegments. The plurality of channel segments may be substantially evenlyspaced apart, for example, around an edge or perimeter of the reservoir.Alternatively, the spacing of the plurality of channel segments may beuneven.

The reservoir 604 may have an expansion angle, a (not shown in FIG. 6)at or near each channel junction. Each channel segment of the pluralityof channel segments 602 may have a width, w, and a height, ho, at ornear the channel junction. The geometric parameters, w, ho, and a, mayor may not be uniform for each of the channel segments in the pluralityof channel segments 602. For example, each channel segment may have thesame or different widths at or near its respective channel junction withthe reservoir 604. For example, each channel segment may have the sameor different height at or near its respective channel junction with thereservoir 604.

The reservoir 604 may have the same or different expansion angle at thedifferent channel junctions with the plurality of channel segments 602.For example, a circular reservoir (as shown in FIG. 6) may have aconical, dome-like, or hemispherical ceiling (e.g., top wall) to providethe same or substantially same expansion angle for each channel segments602 at or near the plurality of channel junctions 606. When thegeometric parameters are uniform, beneficially, resulting droplet sizemay be controlled to be uniform even with the increased throughput. Insome instances, when it is desirable to have a different distribution ofdroplet sizes, the geometric parameters for the plurality of channelsegments 602 may be varied accordingly.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size. The beads and/orbiological particle injected into the droplets may or may not haveuniform size.

FIG. 7A shows a cross-section view of another example of a microfluidicchannel structure with a geometric feature for controlled partitioning.A channel structure 700 can include a channel segment 702 communicatingat a channel junction 706 (or intersection) with a reservoir 704. Insome instances, the channel structure 700 and one or more of itscomponents can correspond to the channel structure 100 and one or moreof its components. FIG. 7B shows a perspective view of the channelstructure 700 of FIG. 7A.

An aqueous fluid 712 comprising a plurality of particles 716 may betransported along the channel segment 702 into the junction 706 to meeta second fluid 714 (e.g., oil, etc.) that is immiscible with the aqueousfluid 712 in the reservoir 704 to create droplets 720 of the aqueousfluid 712 flowing into the reservoir 704. At the junction 706 where theaqueous fluid 712 and the second fluid 714 meet, droplets can form basedon factors such as the hydrodynamic forces at the junction 706, relativeflow rates of the two fluids 712, 714, fluid properties, and certaingeometric parameters (e.g., Δh, etc.) of the channel structure 700. Aplurality of droplets can be collected in the reservoir 704 bycontinuously injecting the aqueous fluid 712 from the channel segment702 at the junction 706.

A discrete droplet generated may comprise one or more particles of theplurality of particles 716. As described elsewhere herein, a particlemay be any particle, such as a bead, cell bead, gel bead, biologicalparticle, macromolecular constituents of biological particle, or otherparticles. Alternatively, a discrete droplet generated may not includeany particles.

In some instances, the aqueous fluid 712 can have a substantiallyuniform concentration or frequency of particles 716. As describedelsewhere herein (e.g., with reference to FIG. 4), the particles 716(e.g., beads) can be introduced into the channel segment 702 from aseparate channel (not shown in FIG. 7). The frequency of particles 716in the channel segment 702 may be controlled by controlling thefrequency in which the particles 716 are introduced into the channelsegment 702 and/or the relative flow rates of the fluids in the channelsegment 702 and the separate channel. In some instances, the particles716 can be introduced into the channel segment 702 from a plurality ofdifferent channels, and the frequency controlled accordingly. In someinstances, different particles may be introduced via separate channels.For example, a first separate channel can introduce beads and a secondseparate channel can introduce biological particles into the channelsegment 702. The first separate channel introducing the beads may beupstream or downstream of the second separate channel introducing thebiological particles.

In some instances, the second fluid 714 may not be subjected to and/ordirected to any flow in or out of the reservoir 704. For example, thesecond fluid 714 may be substantially stationary in the reservoir 704.In some instances, the second fluid 714 may be subjected to flow withinthe reservoir 704, but not in or out of the reservoir 704, such as viaapplication of pressure to the reservoir 704 and/or as affected by theincoming flow of the aqueous fluid 712 at the junction 706.Alternatively, the second fluid 714 may be subjected and/or directed toflow in or out of the reservoir 704. For example, the reservoir 704 canbe a channel directing the second fluid 714 from upstream to downstream,transporting the generated droplets.

The channel structure 700 at or near the junction 706 may have certaingeometric features that at least partly determine the sizes and/orshapes of the droplets formed by the channel structure 700. The channelsegment 702 can have a first cross-section height, h₁, and the reservoir704 can have a second cross-section height, h₂. The first cross-sectionheight, h₁, and the second cross-section height, h₂, may be different,such that at the junction 706, there is a height difference of Δh. Thesecond cross-section height, h₂, may be greater than the firstcross-section height, h₁. In some instances, the reservoir maythereafter gradually increase in cross-section height, for example, themore distant it is from the junction 706. In some instances, thecross-section height of the reservoir may increase in accordance withexpansion angle, β, at or near the junction 706. The height difference,Δh, and/or expansion angle, β, can allow the tongue (portion of theaqueous fluid 712 leaving channel segment 702 at junction 706 andentering the reservoir 704 before droplet formation) to increase indepth and facilitate decrease in curvature of the intermediately formeddroplet. For example, droplet size may decrease with increasing heightdifference and/or increasing expansion angle.

The height difference, Δh, can be at least about 1 μm. Alternatively,the height difference can be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 60,70, 80, 90, 100, 200, 300, 400, 500 μm or more. Alternatively, theheight difference can be at most about 500, 400, 300, 200, 100, 90, 80,70, 60, 50, 45, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11,10, 9, 8, 7, 6, 5, 4, 3, 2, 1 μm or less. In some instances, theexpansion angle, β, may be between a range of from about 0.5° to about4°, from about 0.1° to about 10°, or from about 0° to about 90°. Forexample, the expansion angle can be at least about 0.01°, 0.1°, 0.2°,0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°, 4°, 5°, 6°, 7°,8°, 9°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°,75°, 80°, 85°, or higher. In some instances, the expansion angle can beat most about 89°, 88°, 87°, 86°, 85°, 84°, 83°, 82°, 81°, 80°, 75°,70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°, 20°, 15°, 10°, 9°, 8°,7°, 6°, 5°, 4°, 3°, 2°, 1°, 0.1°, 0.01°, or less.

In some instances, the flow rate of the aqueous fluid 712 entering thejunction 706 can be between about 0.04 microliters (μL)/minute (min) andabout 40 μL/min. In some instances, the flow rate of the aqueous fluid712 entering the junction 706 can be between about 0.01 microliters(μL)/minute (min) and about 100 μL/min. Alternatively, the flow rate ofthe aqueous fluid 712 entering the junction 706 can be less than about0.01 μL/min. Alternatively, the flow rate of the aqueous fluid 712entering the junction 706 can be greater than about 40 μL/min, such as45 μL/min, 50 μL/min, 55 μL/min, 60 μL/min, 65 μL/min, 70 μL/min, 75μL/min, 80 μL/min, 85 μL/min, 90 μL/min, 95 μL/min, 100 μL/min, 110μL/min , 120 μL/min, 130 μL/min, 140 μL/min, 150 μL/min, or greater. Atlower flow rates, such as flow rates of about less than or equal to 10microliters/minute, the droplet radius may not be dependent on the flowrate of the aqueous fluid 712 entering the junction 706. The secondfluid 714 may be stationary, or substantially stationary, in thereservoir 704. Alternatively, the second fluid 714 may be flowing, suchas at the above flow rates described for the aqueous fluid 712.

In some instances, at least about 50% of the droplets generated can haveuniform size. In some instances, at least about 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or greater of the dropletsgenerated can have uniform size. Alternatively, less than about 50% ofthe droplets generated can have uniform size.

While FIGS. 7A and 7B illustrate the height difference, Δh, being abruptat the junction 706 (e.g., a step increase), the height difference mayincrease gradually (e.g., from about 0 μm to a maximum heightdifference). Alternatively, the height difference may decrease gradually(e.g., taper) from a maximum height difference. A gradual increase ordecrease in height difference, as used herein, may refer to a continuousincremental increase or decrease in height difference, wherein an anglebetween any one differential segment of a height profile and animmediately adjacent differential segment of the height profile isgreater than 90°. For example, at the junction 706, a bottom wall of thechannel and a bottom wall of the reservoir can meet at an angle greaterthan 90°. Alternatively or in addition, a top wall (e.g., ceiling) ofthe channel and a top wall (e.g., ceiling) of the reservoir can meet anangle greater than 90°. A gradual increase or decrease may be linear ornon-linear (e.g., exponential, sinusoidal, etc.). Alternatively or inaddition, the height difference may variably increase and/or decreaselinearly or non-linearly. While FIGS. 7A and 7B illustrate the expandingreservoir cross-section height as linear (e.g., constant expansionangle, β), the cross-section height may expand non-linearly. Forexample, the reservoir may be defined at least partially by a dome-like(e.g., hemispherical) shape having variable expansion angles. Thecross-section height may expand in any shape.

The channel networks, e.g., as described above or elsewhere herein, canbe fluidly coupled to appropriate fluidic components. For example, theinlet channel segments are fluidly coupled to appropriate sources of thematerials they are to deliver to a channel junction. These sources mayinclude any of a variety of different fluidic components, from simplereservoirs defined in or connected to a body structure of a microfluidicdevice, to fluid conduits that deliver fluids from off-device sources,manifolds, fluid flow units (e.g., actuators, pumps, compressors) or thelike. Likewise, the outlet channel segment (e.g., channel segment 208,reservoir 604, etc.) may be fluidly coupled to a receiving vessel orconduit for the partitioned cells for subsequent processing. Again, thismay be a reservoir defined in the body of a microfluidic device, or itmay be a fluidic conduit for delivering the partitioned cells to asubsequent process operation, instrument or component.

The methods and systems described herein may be used to greatly increasethe efficiency of single cell applications and/or other applicationsreceiving droplet-based input. For example, following the sorting ofoccupied cells and/or appropriately-sized cells, subsequent operationsthat can be performed can include generation of amplification products,purification (e.g., via solid phase reversible immobilization (SPRI)),further processing (e.g., shearing, ligation of functional sequences,and subsequent amplification (e.g., via PCR)). These operations mayoccur in bulk (e.g., outside the partition). In the case where apartition is a droplet in an emulsion, the emulsion can be broken andthe contents of the droplet pooled for additional operations. Additionalreagents that may be co-partitioned along with the barcode bearing beadmay include oligonucleotides to block ribosomal RNA (rRNA) and nucleasesto digest genomic DNA from cells. Alternatively, rRNA removal agents maybe applied during additional processing operations. The configuration ofthe constructs generated by such a method can help minimize (or avoid)sequencing of the poly-T sequence during sequencing and/or sequence the5′ end of a polynucleotide sequence. The amplification products, forexample, first amplification products and/or second amplificationproducts, may be subject to sequencing for sequence analysis. In somecases, amplification may be performed using the Partial HairpinAmplification for Sequencing (PHASE) method.

A variety of applications require the evaluation of the presence andquantification of different biological particle or organism types withina population of biological particles, including, for example, microbiomeanalysis and characterization, environmental testing, food safetytesting, epidemiological analysis, e.g., in tracing contamination or thelike.

Computer Systems

The present disclosure provides computer systems that are programmed toimplement methods of the disclosure. FIG. 9 shows a computer system 901that is programmed or otherwise configured to, e.g., (i) control amicrofluidics system (e.g., fluid flow), (ii) sort occupied dropletsfrom unoccupied droplets, (iii) polymerize droplets, (iv) performsequencing applications, and/or (v) generate and maintain a library ofbarcoded nucleic acid fragments. The computer system 901 can regulatevarious aspects of the present disclosure, such as, for example,regulating fluid flow rate in one or more channels in a microfluidicstructure, regulating polymerization application units, etc. Thecomputer system 901 can be an electronic device of a user or a computersystem that is remotely located with respect to the electronic device.The electronic device can be a mobile electronic device.

The computer system 901 includes a central processing unit (CPU, also“processor” and “computer processor” herein) 905, which can be a singlecore or multi core processor, or a plurality of processors for parallelprocessing. The computer system 901 also includes memory or memorylocation 910 (e.g., random-access memory, read-only memory, flashmemory), electronic storage unit 915 (e.g., hard disk), communicationinterface 920 (e.g., network adapter) for communicating with one or moreother systems, and peripheral devices 925, such as cache, other memory,data storage and/or electronic display adapters. The memory 910, storageunit 915, interface 920 and peripheral devices 925 are in communicationwith the CPU 905 through a communication bus (solid lines), such as amotherboard. The storage unit 915 can be a data storage unit (or datarepository) for storing data. The computer system 901 can be operativelycoupled to a computer network (“network”) 930 with the aid of thecommunication interface 920. The network 930 can be the Internet, aninternet and/or extranet, or an intranet and/or extranet that is incommunication with the Internet. The network 930 in some cases is atelecommunication and/or data network. The network 930 can include oneor more computer servers, which can enable distributed computing, suchas cloud computing. The network 930, in some cases with the aid of thecomputer system 901, can implement a peer-to-peer network, which mayenable devices coupled to the computer system 901 to behave as a clientor a server.

The CPU 905 can execute a sequence of machine-readable instructions,which can be embodied in a program or software. The instructions may bestored in a memory location, such as the memory 910. The instructionscan be directed to the CPU 905, which can subsequently program orotherwise configure the CPU 905 to implement methods of the presentdisclosure. Examples of operations performed by the CPU 905 can includefetch, decode, execute, and writeback.

The CPU 905 can be part of a circuit, such as an integrated circuit. Oneor more other components of the system 901 can be included in thecircuit. In some cases, the circuit is an application specificintegrated circuit (ASIC).

The storage unit 915 can store files, such as drivers, libraries andsaved programs. The storage unit 915 can store user data, e.g., userpreferences and user programs. The computer system 901 in some cases caninclude one or more additional data storage units that are external tothe computer system 901, such as located on a remote server that is incommunication with the computer system 901 through an intranet or theInternet.

The computer system 901 can communicate with one or more remote computersystems through the network 930. For instance, the computer system 901can communicate with a remote computer system of a user (e.g.,operator). Examples of remote computer systems include personalcomputers (e.g., portable PC), slate or tablet PC's (e.g., Apple® iPad,Samsung® Galaxy Tab), telephones, Smart phones (e.g., Apple® iPhone,Android-enabled device, Blackberry®), or personal digital assistants.The user can access the computer system 901 via the network 930.

Methods as described herein can be implemented by way of machine (e.g.,computer processor) executable code stored on an electronic storagelocation of the computer system 901, such as, for example, on the memory910 or electronic storage unit 915. The machine executable or machinereadable code can be provided in the form of software. During use, thecode can be executed by the processor 905. In some cases, the code canbe retrieved from the storage unit 915 and stored on the memory 910 forready access by the processor 905. In some situations, the electronicstorage unit 915 can be precluded, and machine-executable instructionsare stored on memory 910.

The code can be pre-compiled and configured for use with a machinehaving a processor adapted to execute the code, or can be compiledduring runtime. The code can be supplied in a programming language thatcan be selected to enable the code to execute in a pre-compiled oras-compiled fashion.

Aspects of the systems and methods provided herein, such as the computersystem 901, can be embodied in programming. Various aspects of thetechnology may be thought of as “products” or “articles of manufacture”typically in the form of machine (or processor) executable code and/orassociated data that is carried on or embodied in a type of machinereadable medium. Machine-executable code can be stored on an electronicstorage unit, such as memory (e.g., read-only memory, random-accessmemory, flash memory) or a hard disk. “Storage” type media can includeany or all of the tangible memory of the computers, processors or thelike, or associated modules thereof, such as various semiconductormemories, tape drives, disk drives and the like, which may providenon-transitory storage at any time for the software programming. All orportions of the software may at times be communicated through theInternet or various other telecommunication networks. Suchcommunications, for example, may enable loading of the software from onecomputer or processor into another, for example, from a managementserver or host computer into the computer platform of an applicationserver. Thus, another type of media that may bear the software elementsincludes optical, electrical and electromagnetic waves, such as usedacross physical interfaces between local devices, through wired andoptical landline networks and over various air-links. The physicalelements that carry such waves, such as wired or wireless links, opticallinks or the like, also may be considered as media bearing the software.As used herein, unless restricted to non-transitory, tangible “storage”media, terms such as computer or machine “readable medium” refer to anymedium that participates in providing instructions to a processor forexecution.

Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

The computer system 901 can include or be in communication with anelectronic display 935 that comprises a user interface (UI) 940 forproviding, for example, results of sequencing analysis. Examples of Ulsinclude, without limitation, a graphical user interface (GUI) andweb-based user interface.

Methods and systems of the present disclosure can be implemented by wayof one or more algorithms. An algorithm can be implemented by way ofsoftware upon execution by the central processing unit 905. Thealgorithm can, for example, perform sequencing.

Devices, systems, compositions and methods of the present disclosure maybe used for various applications, such as, for example, processing asingle analyte (e.g., RNA, DNA, or protein) or multiple analytes (e.g.,DNA and RNA, DNA and protein, RNA and protein, or RNA, DNA and protein)from a single cell. For example, a biological particle (e.g., a cell orcell bead) is partitioned in a partition (e.g., droplet), and multipleanalytes from the biological particle are processed for subsequentprocessing. The multiple analytes may be from the single cell. This mayenable, for example, simultaneous proteomic, transcriptomic and genomicanalysis of the cell.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is not intendedthat the invention be limited by the specific examples provided withinthe specification. While the invention has been described with referenceto the aforementioned specification, the descriptions and illustrationsof the embodiments herein are not meant to be construed in a limitingsense. Numerous variations, changes, and substitutions will now occur tothose skilled in the art without departing from the invention.Furthermore, it shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is therefore contemplated that theinvention shall also cover any such alternatives, modifications,variations or equivalents. It is intended that the following claimsdefine the scope of the invention and that methods and structures withinthe scope of these claims and their equivalents be covered thereby.

What is claimed is: 1.-34. (canceled)
 35. A method comprising: a)fragmenting chromatin to generate a plurality of chromatin fragments; b)tagging said plurality of chromatin fragments with a first tag togenerate a plurality of first tagged chromatin fragments; c) binding anaffinity molecule to a protein or a peptide associated with at least onetagged chromatin fragment of said plurality of first tagged chromatinfragments, wherein said affinity molecule is coupled to a second tag;and d) coupling said first tag to said second tag to generate a secondtagged chromatin fragment, wherein said fragmenting of a) and saidtagging of b) comprise a tagmentation reaction.
 36. The method of claim35, further comprising, e) sequencing said second tagged chromatinfragment.
 37. The method of claim 36, further comprising, prior to e),amplifying said second tagged chromatin fragment.
 38. The method ofclaim 35, wherein said tagmentation reaction is performed by atransposase.
 39. The method of claim 38, wherein said transposase isselected from the group consisting of: a hyperactive Tn5 transposase, aMuA transposase, a Vibhar transposase, and Hermes.
 40. The method ofclaim 35, wherein said first tag is a first oligonucleotide tag and saidsecond tag is a second oligonucleotide tag.
 41. The method of claim 40,wherein said coupling of d) comprises ligating said firstoligonucleotide tag to said second oligonucleotide tag.
 42. The methodof claim 41, wherein said ligating further comprises: i) annealing afirst region of said first oligonucleotide tag to a first region of saidsecond oligonucleotide tag, wherein said first region of said firstoligonucleotide tag is complementary to said first region of said secondoligonucleotide tag; and ii) ligating said first oligonucleotide tag tosaid second oligonucleotide tag.
 43. The method of claim 41, whereinsaid ligating further comprises: i) annealing a first region of a thirdoligonucleotide tag to a region of said first oligonucleotide tag,wherein said first region of said third oligonucleotide tag iscomplementary to said region of said first oligonucleotide tag; ii)annealing a second region of said third oligonucleotide tag to a regionof said second oligonucleotide tag, wherein said second region of saidthird oligonucleotide tag is complementary to said region of said secondoligonucleotide tag; and iii) ligating said third oligonucleotide tag tosaid first oligonucleotide tag and said second oligonucleotide tag. 44.The method of claim 43, wherein said third oligonucleotide tag comprisesa unique molecular index, a cell barcode, or both.
 45. The method ofclaim 44, wherein said third oligonucleotide tag is attached to asurface of a bead.
 46. The method of claim 45, wherein said thirdoligonucleotide tag is releasably attached to said surface of said bead.47. The method of claim 46, wherein said bead comprises a plurality ofthird oligonucleotides, each of said plurality of third oligonucleotidescomprising: i) a first barcode unique for each individual first taggedchromatin fragment binding thereon; and ii) a second barcode unique tosaid bead.
 48. The method of claim 35, further comprising, prior to d),partitioning a plurality of cells or cell nuclei into a plurality ofpartitions, wherein each partition of said plurality of partitionscomprises a single cell or cell nucleus.
 49. The method of claim 48,further comprising, prior to d), partitioning said bead into a pluralityof partitions, such that each partition of said plurality of partitionscontains a single bead.
 50. The method of claim 49, further comprising,attaching one or more sequencing adapters to said second taggedchromatin fragment prior to said sequencing of e).
 51. The method ofclaim 35, wherein said first tag is attached to a first end of saidplurality of first tagged nucleic acid fragments, said first tag isattached to a second end of said plurality of first tagged nucleic acidfragments, or both.
 52. The method of claim 35, wherein said affinitymolecule is selected from the group consisting of: an antibody or anantibody fragment, a protein, a peptide, and an aptamer.
 53. The methodof claim 35, wherein said protein or peptide associated with said atleast one tagged nucleic acid fragment is a transcription factor, ahistone, a histone modification, an epigenetic regulator, or anycombination thereof.
 54. The method of claim 35, wherein said second tagcomprises an affinity molecule barcode.